Adhesion molecules on the endothelium and mononuclear cells in human atherosclerotic lesions.

Atherosclerotic lesions show features of a cell-mediated immune inflammatory process. From this viewpoint, the potential role of arterial endothelium in the recruitment of mononuclear cells (T lymphocytes and macrophages) was studied. The endothelium of diffuse intimal thickening (DIT) and atheromatous plaques (AP) in human coronary arteries and abdominal aortas was characterized for the expression of adhesion molecules ELAM-1, ICAM-1, and the major histocompatibility complex (MHC) class II antigens HLA-DR/DP. A marked increase in expression of ICAM-1 and ELAM-1, and to a lesser extent HLA-DR/DP was observed on endothelial cells that were adjacent to subendothelial infiltrates of T lymphocytes (CD3+, CD11a+, HLA-DR/DP+) and macrophages (CD14+, CD11a+, CD11c+, HLA-DR/DP+). This contrasted with a lower or absent expression of these activation markers at sites without prominent inflammatory cell infiltrates. These findings could be demonstrated in DIT as well as in AP. The observations suggest that cytokines produced by the subintimal infiltrates may activate the endothelium in a similar way as is observed in the microvasculature at sites of immune inflammation. The expression of these activation markers in the microvasculature is associated with enhanced leukocyte adhesion, permeability for macromolecules, and procoagulant activity, features known to occur also in early experimental atherosclerosis. The findings therefore support the concept that arterial endothelium plays an active role in the recruitment of mononuclear cells in atherosclerotic lesions.     

Human coronary transplantation-associated arteriosclerosis. Evidence for a chronic immune reaction to activated graft endothelial cells

Occlusive disease of coronary arteries of engrafted hearts is the major obstacle to long-term survival of human cardiac allografts. The pathogenesis of this process remains uncertain. The identity and localization of cells found in transplantation-associated arteriosclerosis lesions from human cardiac allografts were evaluated, and their expression of class II major histocompatibility complex (human leukocyte antigen-DR [HLA-DR]), surface molecules required for recognition of foreign cells by CD4+ T lymphocytes, was noted. Expanded intimas of transplanted coronary arteries contain T lymphocytes (both CD4+ and CD8+ in approximately equal number) and HLA-DR+ macrophages, both localized primarily in a ring immediately below the luminal endothelium, a distribution strikingly different from that in typical atherosclerosis. Coronary arterial endothelium from six of six transplanted hearts studied bore high levels of HLA-DR. Normal human arteries or usual atherosclerotic lesions have few if any HLA-DR+ endothelial cells. The significance of these findings was tested by evaluating the ability of HLA-DR+ arterial cells to interact with allogeneic T cells in vitro. Endothelial cells (but not smooth muscle cells) cultured from human arteries stimulated foreign CD4+ T cells to proliferate and augmented their secretion of interleukin-2. These findings suggest that ongoing stimulation of recipient T lymphocytes by HLA-DR+ endothelium of donor coronary arteries contributes to a sustained regional immune response. Consequent local release of cytokines may regulate smooth muscle cell proliferation and matrix accumulation within the coronary arteries of allografted hearts.     

Class II MHC antigen expression in the atherosclerotic plaque: smooth muscle cells express HLA-DR, HLA-DQ and the invariant gamma chain

Class II antigens of the major histocompatibility complex (MHC) are normally expressed only by cells of the immune system. They may, however, also appear on other cells, both in vivo and in vitro. We have studied class II MHC antigen expression on human arterial smooth muscle cells using immunocytochemical analysis of surgical biopsies. The class II antigens, HLA-DQ and HLA-DR are virtually absent from cells of normal arteries, but appear in atherosclerotically transformed tissue, where the majority of cells express HLA-DR, and one-third of the cells express HLA-DQ. These atherosclerotic plaques are composed of a heterogeneous population of cells, which includes smooth muscle cells, macrophages, and T cells. Among smooth muscle cells containing the muscle-specific intermediate filament protein desmin, one-third of the cells express HLA-DR and almost as many express HLA-DQ. These cells also contain the invariant gamma chain, which is associated with class II antigens during intracellular transport. Plaque macrophages, in contrast, are usually of the DQ-DR+ phenotype. The patterns of class II antigen expression are discussed in relation to cell differentiation and pathogenesis of disease.     

Immunopathology of skin lesions in Kawasaki disease]

Histopathological findings of skin lesions in Kawasaki disease (KD) have been characterized by extensive edema associated with the dilatation of small vessels in the papillary dermis. Although the inflammation in KD skin lesions was exudative in nature, neutrophil emigration was slight and most of the infiltrates were mononuclear cells. Immunofluorescent studies using skin biopsy specimens from 10 patients with KD aged from six months to eight years and seven months showed that the infiltrating cells in the dermis and epidermis were mainly composed of CD 3+ T cells and Leu M3+ macrophages, but not B cells. In double immunofluorescence staining with combinations of anti HLA-DR, CD4 and CD8 monoclonal antibodies, the infiltrating T cells were mainly CD4+ HLA-DR+ T cells. Leu 23% cell were also positive on these cells, thereby suggesting those to be activated. Studies of skin specimens obtained from the site of BCG vaccinations in patients with KD showed basically similar but more extensive lesions. As a control, the infiltrating cells in the dermis from patients with measles were examined. In contrast to KD, these cells were mainly CD8+ T cells. Together with the findings that the keratinocytes in the epidermis were positive for HLA-DR, the skin lesions in KD appear to be similar to those found in delayed type hypersensitivity. Thus, macrophages and helper T cells may play a crucial role in the pathogenesis of KD.     

Mononuclear cells in acute allograft glomerulopathy.

A distinctive glomerular lesion of renal allografts, acute allograft glomerulopathy (AAG), is characterized by hypercellularity and endothelial cell hypertrophy and injury. For elucidating the pathogenesis of this lesion, the infiltrating cells were analyzed by light- and electron-microscopic immunoperoxidase techniques with monoclonal antibodies and compared with those in cellular rejection without AAG (non-AAG). Substantial numbers of T lymphocytes (CD3+,Leu-4+) were detected in the glomeruli in AAG (11.4 +/- 2.4 cells per glomerular cross-section), whereas very few were found in non-AAG (1.4 +/- 1.8, P less than 0.001). In AAG the CD8+ (Leu-2a) subset accounted for essentially all of the intraglomerular T cells, which had a lower CD4/CD8 ratio than the corresponding peripheral blood lymphocytes (P less than 0.03). AAG also differed from non-AAG by the accumulation of intraglomerular mononuclear cells that expressed HNK-1 antigen (Leu-7) and mononuclear phagocytes, which were identified by the presence of the monocyte fibronectin receptor (A6F10). Intraglomerular mononuclear cells were positive for the interleukin-2 receptor (IL2R) and HLA Class II antigens (HLA-DR). The glomeruli in AAG stained more intensely for HLA Class I antigens than the tubules, in contrast to non-AAG cases (P less than 0.03). The interstitial infiltrates in AAG grafts were less intense than in non-AAG of similar duration (P less than 0.01) and had a lower CD4/CD8 ratio, whereas arterial intimal infiltrates were more severe in AAG (P less than 0.03) and consisted of CD8+, but not CD4+, cells. Pathologic features that correlated with poor graft survival were increased numbers of intraglomerular CD8+ cells (both AAG and non-AAG), fewer interstitial T cells (AAG), and more interstitial CD8+ cells (non-AAG) (all P less than 0.05). Cytomegalovirus (CMV) infection was detected in all (8/8) patients with AAG who were studied for infection before or within 3 weeks after the biopsy, compared with 3 of 9 patients with non-AAG. It is proposed that acute allograft glomerulopathy is a distinct form of T-cell-mediated allograft rejection, sometimes associated with CMV infection, in which the glomerular endothelium, often with the arterial endothelium, becomes the principal target of CD8+ T cells.     

Immunohistochemical study of human placental stromal cells

An immunohistochemical study of stromal cells in human placental villi was made using various polyclonal and monoclonal antibodies. This study demonstrated that almost all villous stromal cells expressed HLA-ABC, which is indicative of class I major histocompatibility complex, and vimentin, which is a mesenchymal marker, through the entire period of pregnancy. Some of these stromal cells were considered to be fetal macrophages having HLA-DR, which is a determinant of class II major histocompatibility complex, particularly in the second and third trimesters. Such macrophages also expressed CD-4 (Leu-3a and -3b) and 2H4, which are the cell membrane determinants of suppressor-inducer T lymphocyte; CD-2 (Leu-5b), which is a marker of pan-T cell; Leu-M3, Leu-M5 and Mac-1, which are the markers of monocyte and macrophage lineage; leukocyte common antigen, which is a marker of bone marrow derived cell; and alpha-antichymotrypsin, which is a glycoprotein associated with macrophages. Morphologically, villous macrophages consisted of heterogeneous phenotypes such as classic Hofbauer cells, fibroblast-like spindle cells with long cytoplasmic processes, and dendritic-shaped cells. These may have more complex features than previously considered and may have a greater initiating role in immunologic interactions between mother and fetus when compared with the very sparsely distributed T or B lymphocytes.     

Detection of activated T lymphocytes in the human atherosclerotic plaque

It was recently shown that the human atherosclerotic plaque contains significant amounts of T lymphocytes, and also that smooth muscle cells in these plaques express class II MHC (Ia) antigens. These antigens are not normally present on smooth muscle cells but are inducible by interferon-gamma, a secretory product of activated T cells. Therefore, T cell activation in the plaque was analyzed by immunofluorescent detection of activation markers on T cells isolated from the plaques and in cryostat sections of carotid endarterectomy specimens. Of cells isolated from the plaque, 5% exhibited the E rosettes characteristic of T cells. One third of these cells expressed HLA-DR and VLA-1 (very late activation antigen-1), which in T cells are synthesized only in the activated state. T cells were also identified in sections using immunofluorescent detection of the T cell-specific surface protein, CD3 (Leu-4), with rhodamine labeled second-step antibodies. The frequency of activated T cells was then determined by staining the same, or serial, sections with antibodies to HLA-DR or to the interleukin-2 receptor, followed by biotin-avidin-FITC detection. Of the T cells in the plaque, 34% and 6%, respectively, expressed these cell surface proteins. Taken together, these results indicated that a substantial proportion of the T cells in atherosclerotic plaque are in an activated state. The activation pattern, with a high frequency of HLA-DR and VLA-1 expression and a much lower frequency of interleukin-2 receptor expression, was similar to that reported to occur in chronic inflammatory conditions. Interferon-gamma could be detected in and around some of the lymphocytes, suggesting that paracrine secretion of this lymphokine may occur in the plaque. T cells may be activated locally, presumably by antigen(s) presented in the context of class II MHC expressing smooth muscle cells and/or macrophages, in the atherosclerotic lesion. Such activated T cells may in turn modulate the functions of other cells in the plaque.     

Immunohistology of oral lesions from patients with recurrent oral ulcers and Behçet's syndrome

A qualitative and quantitative immunohistological investigation was performed on biopsies of oral ulcers from patients with Behcet's syndrome (BS) and those with recurrent oral ulcers (ROU). The results were compared with control oral biopsies from patients with other diseases and normal oral mucosa. The expression of HLA-DR on the cell membrane of keratinocytes was found in 13 out of 15 lesions from patients with BS and ROU, as compared with only one out of 15 controls. The relative density of HLA-DR was investigated quantitatively by microdensitometry and this confirmed that DR expression in the epithelial cells of patients with BS and ROU was significantly greater than in diseased and normal control oral tissues. A prominent mononuclear cell infiltration consisted predominantly of T lymphocytes and mature macrophages. Analysis of the CD4 and CD8 subsets of T cells failed to show significant differences between BS, ROU and control diseased tissues. Increased numbers of Langerhans cells were found in the epithelium by morphometric analysis with the CD1 monoclonal antibody in BS and ROU but an increased number was also found in lichen planus. The results suggest that the immunohistological changes in oral lesions of BS and ROU manifest an enhanced immune response in the epithelium, keratinocytes express HLA-class II antigen and increased number of Langerhans cells as well as in the lamina propria with a prominent infiltration of CD4, CD8 and macrophage-like cells. The characteristic pattern of exacerbations and remissions of oral ulceration can be interpreted by the hypothesis that an initiating microbial agent may induce a mononuclear cell infiltration, with the release of cytokines, expression of class II antigen in keratinocytes and causing ulceration, followed by down-regulation of immunity by tolerant T cells induced by the class II positive keratinocytes, leading to a remission.     

A recombinant single-chain human class II MHC molecule (HLA-DR1) as a covalently linked heterotrimer of α chain, β chain,and antigenic peptide,with immunogenicity in vitro and reduced affinity for bacterial superantigens

Major histocompatibility complex (MHC) class II molecules bind to numerous peptides and display these on the cell surface for T cell recognition. In a given immune response, receptors on T cells recognize antigenic peptides that are a minor population of MHC class II-bound peptides. To control which peptides are presented to T cells, it may be desirable to use recombinant MHC molecules with covalently bound antigenic peptides. To study T cell responses to such homogenous peptide-MHC complexes, we engineered an HLA-DR1 cDNA coding for influenza hemagglutinin, influenza matrix, or HIV p24 gag peptides covalently attached via a peptide spacer to the N terminus of the DR1 β chain. Co-transfection with DR α cDNA into mouse L cells resulted in surface expression of HLA-DR1 molecules that reacted with monoclonal antibodies (mAb) specific for correctly folded HLA-DR epitopes. This suggested that the spacer and peptide did not alter expression or folding of the molecule. We then engineered an additional peptide spacer between the C terminus of a truncated β chain (without transmembrane or cytoplasmic domains) and the N terminus of full-length DR α chain. Transfection of this cDNA into mouse L cells resulted in surface expression of the entire covalently linked heterotrimer of peptide, β chain, and α chain with the expected molecular mass of approximately 66 kDa. These single-chain HLA-DR1 molecules reacted with mAb specific for correctly folded HLA-DR epitopes, and identified one mAb with [MHC + peptide] specificity. Affinity-purified soluble secreted single-chain molecules with truncated α chain moved in electrophoresis as compact class II MHC dimers. Cell surface two-chain or single-chain HLA-DR1 molecules with a covalent HA peptide stimulated HLA-DR1-restricted HA-specific T cells. They were immunogenic in vitro for peripheral blood mononuclear cells. The two-chain and single-chain HLA-DR1 molecules with covalent HA peptide had reduced binding for the bacterial superantigens staphylococcal enterotoxin A and B and almost no binding for toxic shock syndrome toxin-1. The unique properties of these engineered HLA-DR1 molecules may facilitate our understanding of the complex nature of antigen recognition and aid in the development of novel vaccines with reduced superantigen binding.     

Sequential induction of MHC antigens on autochthonous cells of ileum affected by Crohn''s disease.

Changes were examined in the expression of Class I and II major histocompatibility complex (MHC) antigens by autochthonous cells of the terminal ileum affected by Crohn's disease. The study was based on the analysis of transmural specimens from terminal ileum segments obtained in the course of ileocolectomy for colon cancer and Crohn's disease. Serial sections were immunostained using monoclonal antibodies directed against monomorphic determinants of HLA-A,B,C, DR, DP, DQ, and the invariant chain (Ii) associated with Class II molecules. Compared with the normal state, the only change in Class I antigen expression occurring in Crohn's disease was the induction of HLA-A,B,C antigens in lymphatic endothelium. Changes in Class II antigen expression were more substantial. Enhancement of HLA-DR expression was found in enterocytes; DR induction was observed in glial cells of the visceral nervous plexus and in venular and venous endothelium. HLA-DP and DQ antigens were induced in enterocytes, glial cells, and capillary and venular endothelium, although this induction was restricted to areas of moderate or high inflammatory activity. The tissue distribution of Ii closely resembled that of HLA-DR, although this association was not strict: on the one hand, arterial endothelium contained low amounts of Ii in the absence of DR antigens; on the other hand, glial cells expressed Class II molecules in the absence of Ii. The extent of local enhancement/induction of MHC antigens was positively correlated with the local density of the cellular infiltrate. These data suggest that altered MHC antigen expression by autochthonous structures might be mediated by factors released from the lymphohistiocytic infiltrate, which is itself attracted by an unknown signal. In conjunction with an unknown antigen, the enhanced expression of Class II antigens might trigger an autoaggressive immune response.     

Nonimmune human cells can express MHC class II antigens in the absence of invariant chain--an immunohistological study on normal and chronically inflamed small intestine

The expression of HLA-DR, HLA-DP and HLA-DQ antigens and of the associated invariant chain (Ii) was studied immunohistologically in sessile cells of normal ileum and ileum affected by Crohn's disease which was taken as a model for chronic inflammation. Corresponding to the local inflammatory cell density, a considerable neo-expression of MHC class II antigens and Ii was observed in epithelial cells, vascular endothelial cells, and Schwann cells of the enteric nerve plexus. While HLA-DP and HLA-DQ antigens were undetectable in sessile cells of normal ileum, class II antigens expression in ileitis followed the order HLA-DR greater than or equal to HLA-DP greater than or equal to HLA-DQ. In various cell types a differential expression of Ii and class II antigens was noted. In normal crypt enterocytes and in arterial endothelial cells of inflamed ileum, Ii was found in the absence of class II antigens. On the other hand, most Schwann cells and internodal nerve strands of the submucous and myenteric plexus exhibited HLA-DR (-DP, -DQ) antigens in the absence of detectable Ii. Moreover, HLA-DR+ endothelial cells in normal tissue specimens were Ii-, and in inflamed intestine HLA-DR expression of venous/venular and capillary endothelium greatly exceeded Ii expression. The observation of both Ii+/HLA-DR- and Ii-/HLA-DR+ (HLA-DP+, HLA-DQ+) cells questions the previously assumed close association of Ii and class II antigen expression.     

Activated myeloid dendritic cells accumulate and co-localize with CD3+ T cells in coronary artery lesions in patients with Kawasaki disease

Emerging evidence implicating the participation of dendritic cells (DCs) and T cells in various vascular inflammatory diseases such as giant cell arteritis, Takayasu's arteritis, and atherosclerosis led us to hypothesize that they might also participate in the pathogenesis of coronary arteritis in Kawasaki disease (KD). Coronary artery specimens from 4 patients with KD and 6 control patients were obtained. Immunohistochemical and computer-assisted histomorphometric analyses were performed to detect all myeloid DCs (S-100(+), fascin(+)), all plasmacytoid DCs (CD123(+)) as well as specific DC subsets (mature myeloid DCs [CD83(+)], myeloid [BDCA-1(+)] and plasmacytoid DC precursors [BDCA-2(+)]), T cells (CD3(+)), and all antigen-presenting cells (HLA-DR(+)). Co-localization of DCs with T cells was assessed using double immunostaining. Significantly more myeloid DCs at a precursor, immature or mature stage were found in coronary lesions of KD patients than in controls. Myeloid DC precursors were distributed equally in the intima and adventitia. Mature myeloid DCs were particularly abundant in the adventitia. There was a significant correlation between mature DCs and HLA-DR expression. Double immunostaining demonstrated frequent contacts between myeloid DCs and T cells in the outer media and adventitia. Plasmacytoid DC precursors were rarely found in the adventitia. In conclusion, coronary artery lesions of KD patients contain increased numbers of mature myeloid DCs with high HLA-DR expression and frequent T cell contacts detected immunohistochemically. This suggests that mature arterial myeloid DCs might be activating T cells in situ and may be a significant factor in the pathogenesis of coronary arteritis in KD.     

CD1 Expression in Human Atherosclerosis : A Potential Mechanism for T Cell Activation by Foam Cells

Atherosclerotic plaques are chronic inflammatory lesions composed of dysfunctional endothelium, smooth muscle cells, lipid-laden macrophages, and T lymphocytes. This study analyzed atherosclerotic tissue specimens for expression of CD1 molecules, a family of cell surface proteins that present lipid antigens to T cells, and examined the possibility that CD1+ lipid-laden macrophages might present antigen to T cells. Immunohistochemical studies using a panel of specific monoclonal antibodies demonstrated expression of each of the four previously characterized human CD1 proteins (CD1a, -b, -c, and -d) in atherosclerotic plaques. Expression of CD1 was not observed in normal arterial specimens and appeared to be restricted to the CD68+ lipid-laden foam cells of atherosclerotic lesions. CD1 molecules colocalized in areas of the arterial wall that also contained abundant T lymphocytes, suggesting potential interactions between CD1+ cells and plaque-infiltrating lymphocytes in situ. Using CD1-expressing foam cells derived from macrophages in vitro, we demonstrated the ability of such cells to present lipid antigens to CD1 restricted T cells. Given the abundant T cells, CD1+ macrophages, and lipid accumulation in atherosclerotic plaques, we propose a potential role for lipid antigen presentation by CD1 proteins in the generation of the inflammatory component of these lesions.     

Cytotoxic Human HLA Class II Restricted Purified Protein Derivative-Reactive T-Lymphocyte Clones

Human T-lymphocyte clones specific for antigenic components of purified protein derivative (PPD) of tuberculin were generated by limiting dilution using in vitro PPD-activated peripheral blood mononuclear cells from a single donor. The HLA restriction specificity of eight clones that were cytotoxic against autologous PPD-pulsed monocyte targets, was examined against a panel of allogeneic PPD pulsed targets. In agreement with our findings with bulk-expanded PPD-reactive cytotoxic T lymphocytes, all clones were restricted by HLA class II antigens: seven by HLA-DR 2 and one by HLA-DRw10--the other HLA-DR antigen of the donor. All clones were CD3+, CD4+, CD8-. One clone exhibited, in addition to HLA-DR2 restriction, unrestricted cytotoxic alloreactivity against HLA-DR1. In monoclonal antibody-blocking experiments the latter clone was the only one that was blocked. Its lytic ability was abolished by two monoclonal antibodies against monomorphic HLA-DR determinants. The antigen specificity of the clones was studied by using autologous monocyte targets pulsed with antigens prepared from a range of different mycobacterial species. All seven HLA-DR2-restricted clones reacted with the majority of antigens tested. In contrast, the HLA-DRw10-restricted clone reacted exclusively with an antigen unique to PPD.     

Expression of immune system-associated antigens by cells of the human central nervous system: relationship to the pathology of Alzheimer's disease

HLA-DR is a class II major histocompatibility complex antigen which in the periphery confers antigen presenting capability. We have previously shown that this marker is profusely expressed in cortex of elderly and Alzheimer's disease (AD) patients, as is the receptor for the lymphokine interleukin-2. We now report presence of additional immune-related antigens in AD, and distributional differences from normal elderly controls. In gray matter, HLA-DR immunoreactivity is normally sparse, except in AD where it co-localizes with virtually all neuritic plaques. HLA-DR positive T cells can be demonstrated in Alzheimer's disease brain tissue, as can instances of apposition between putative brain microglia and T cells. In addition, cells with the morphologic characteristics of astrocytes label for natural killer cell antigen (Leu-11), and apparent lymphocytes bearing T helper and T cytotoxic/suppressor cell antigens are observed. These and other data suggest that the glial proliferation and scavenger activity characteristic of Alzheimer's disease may occur in an immune context and may play an important role in the pathogenesis of the disorder.     

Identification of mononuclear cells and T cell subsets in rheumatic valvulitis

The composition of the mononuclear cellular filtrates was investigated in 13 valve specimens from nine patients with rheumatic carditis, some of whom had clinical and laboratory evidence of acute disease at the time of surgery. In acute valvulitis (AV) as well as in chronic active valvulitis (CAV), the cellular infiltrates were primarily composed of T cells and macrophages. In AV the majority of these T cells were of the helper phenotype (Leu 3a). The T cells subsets were more heterogeneous in CAV. In five valves, the helper T cells exceeded the number of suppressor T cells, whereas in three others, helper and cytotoxic/suppressor T cells were present in equal numbers. The HLA-DR antigen was expressed by the majority of the mononuclear cells and by the vascular endothelium. These findings indicate that the valvular injury may at least in part be mediated by delayed-type hypersensitivity mechanisms. Those cells comprising the Aschoff body were primarily positive for the HLA-DR and a novel monoclonal antibody called D8/17 which identifies an antigen known to be present on the B cells of rheumatic fever patients.     

Class II antigens on canine T lymphocytes

A panel of crossreactive anti-human, -mouse and -rat MHC class II monoclonal antibodies (Mabs) was used to examine MHC class II antigen expression on canine T lymphocytes by cytofluorometry. The presence of MHC class II antigens was demonstrated on activated T lymphoblasts as well as on non-stimulated peripheral blood T lymphocytes. A number of anti-MHC class II Mabs reacted only with activated T lymphoblasts. Immunoprecipitation studies confirmed the Ia-like or MHC class II molecular character of the antigens on canine T cells. The expression of MHC class II antigens on peripheral blood T lymphocytes appeared to be not induced by stimulation of the T cells, as purified T lymphocytes of specific pathogen free dogs reacted with anti-MHC class II Mabs. Moreover, the study indicates that MHC class II antigen expression is present in the neonatal thymus. Lectin stimulated and allogeneically stimulated T lymphoblasts showed a stronger expression of MHC class II antigens in comparison with non-stimulated T cells.     

An immunohistological study of the cellular constituents of Hodgkin''s disease using a monoclonal antibody panel

Cryostat sections of lymphoid tissue from 44 cases of Hodgkin's disease were analysed by immunoperoxidase staining using a panel of monoclonal antibodies which included reagents reactive with T cells and their subsets, B cells, HLA-DR, Ig, dendritic reticulum cells and C3b receptor. A wide spectrum of immunohistological patterns was observed ranging from cases in which T cells were numerous (B cells being absent or present in only small numbers) to cases in which very prominent B cell follicles were present. These follicles contained a meshwork of dendritic reticulum cells and were composed of polyclonal B cells (as assessed by light chain expression). T cells were present in small numbers within these B cell follicles, often clustered in a thin rim around individual Reed-Sternberg and Hodgkin's cells. All B cell-rich cases were examples of lymphocyte predominant Hodgkin's disease. Assessment of the T cell helper/suppressor ratios was hindered by the fact that both anti-helper antibodies (OKT4 and anti-Leu 3a) reacted with macrophages. However the majority of cases appeared to contain a normal excess of T helper cells. HLA-DR was strongly expressed in T cell rich areas, on Reed-Sternberg and Hodgkin's cells, on vascular endothelium and on numerous infiltrating cells in the fibrous tissue areas in cases of nodular sclerosing disease. Reed-Sternberg and Hodgkin's cells were not labelled by either anti-fibronectin or by antibodies reactive with dendritic reticulum cells (anti-C3b receptor and antibody R4/23).     

Human Th1 cell lines recognize the Mycobacterium tuberculosis ESAT-6 antigen and its peptides in association with frequently expressed HLA class II molecules

We have used a synthetic-peptide approach to map epitope regions of the Mycobacterium tuberculosis ESAT-6 antigen recognized by human T cells in relation to major histocompatibility complex (MHC) restriction. ESAT-6-specific CD4+ T-cell lines were established by stimulating peripheral blood mononuclear cells from 25 HLA-DR-typed tuberculosis patients with complete antigen in vitro. The established T-cell lines were then screened for proliferation and interferon-gamma (IFN-gamma) secretion in response to eight overlapping 20-mer peptides covering the ESAT-6 sequence. The response of the T-cell lines to ESAT-6 and peptides from a human leucocyte antigen (HLA)-heterogeneous group of donors suggested the presence of multiple epitopes and promiscuous recognition of the antigen. Analysis of antigen and peptide recognition in the presence of anti-HLA class I and class II antibodies suggested that the T-cell lines recognized ESAT-6 in association with HLA-DR and -DQ molecules. Furthermore, testing of selected T-cell lines with ESAT-6 and the peptides in the presence of autologous and allogeneic HLA-DR- and -DQ-typed antigen-presenting cells identified HLA-DR2, -DR52 and -DQ2 amongst the HLA molecules involved in the presentation of ESAT-6 and its peptides to human Th1 cells. In addition, the T-cell lines were cytotoxic for monocytes and macrophages pulsed with ESAT-6 and peptides. In conclusion, the recognition of ESAT-6 by IFN-gamma-secreting and cytotoxic CD4+ T cells in association with frequently expressed HLA class II molecules supports the application of this antigen to either specific diagnosis or subunit vaccine design.