Accumulation of CTLA-4 expressing T lymphocytes in the germinal centres of human lymphoid tissues.

CTLA-4, a coreceptor with sequence homology to CD28 is expressed on T cells after activation. Mice deficient for CTLA-4 die young from massive infiltration of many organs by activated T cells, which highlights the essential inhibitory role the coreceptor plays in the regulation of the immune response. To study the prevalence and distribution of CTLA-4 in situ immunohistological analyses were carried out on human tonsils and lymph nodes. Expression of CTLA-4 was restricted to alpha beta T cells, and CTLA-4+ B cells were not observed. In T-cell areas, 2-10% of T cells were positive for CTLA-4 with similar percentages in the CD4+ and CD8+ subpopulations. In the germinal centres (GC) the fraction of CTLA-4+ T cells was much higher (70-90%). This was due to frequent expression of CTLA-4 on the CD4+ helper subpopulation. GC CD8+ T cells were rare and mostly did not express the coreceptor. The CTLA-4+ T-cell fraction was also over-represented among intraepithelial tonsillar T cells. Cycling (Ki-67+) and apoptotic (TUNEL+) T cells were never positive for CTLA-4, while a subset of CD25+ cells did express the coreceptor. Since CTLA-4 is essential for the physiological limitation of the immune response, GC T cells, which are mostly CTLA-4 positive, might be important in this process.     

T lymphocytes expressing HECA-452 epitope are present in cutaneous acute graft-versus-host disease and erythema multiforme, but not in acute graft-versus-host disease in gut organs.

Lymphocytes in formalin-fixed skin biopsies from patients with cutaneous acute graft-versus-host disease (aGVHD) were studied with HECA-452 (an antibody recognizing lymphocytes with skin-homing properties) and a panel of antibodies recognizing pan-B (L26 [CD20]), pan-T (L60 [CD43] and A6 [CD45RA]), and T-helper subset (OPD4) antigens in paraffin sections. Biopsies from patients with erythema multiforme (EM) were similarly studied for comparison. In both conditions, T lymphocytes stained by OPD4 were predominantly confined to the dermis, whereas those stained by HECA-452 were concentrated in the epidermis; however, there was considerable variation between cases, and overlap between findings in the dermis and epidermis. Lymphocytes similarly studied in paraffin sections of liver, salivary gland, and gut affected by aGVHD were essentially unreactive with HECA-452, although they were largely stained by pan-T markers and showed some comparable reactivity with OPD4. The findings suggest that aGVHD of the skin is mediated by a different set of lymphocytes than in gut organs, and may have a similar immunologic mechanism to EM.     

Progressive transformation of germinal centers with and without association to Hodgkin's disease

Progressively transformed germinal centers occurred in about 3.5% of cases of chronic nonspecific lymphadenitis. They are larger than germinal centers and are composed of follicular mantle lymphocytes, small clusters of proliferating mainly medium-sized B- and T-cells, as well as an extensive network of follicular dendritic cells. Sixty-six patients with lymph node enlargement containing progressively transformed germinal centers and staging and sequential biopsies of 213 patients with Hodgkin's disease (mixed and nodular sclerosis type) were investigated with special reference to the relationship of this lesion to Hodgkin's disease. In most cases, progressively transformed germinal centers developed without any obvious signs of illness and seemed to have no association with Hodgkin's disease. The patients could be differentiated into two groups. The larger group, Group 1 (n = 55 of 66) consisted of patients showing progressively transformed germinal centers without association to Hodgkin's disease. The smaller group, Group 2 (n = 11 of 66) showed progressively transformed germinal centers obviously with association to nodular paragranuloma (Hodgkin's disease lymphocytic predominance type). Progressively transformed germinal centers preceding (n = 3), simultaneously (n = 4), and after development of nodular paragranuloma (n = 4) were found. With regard to subtypes of Hodgkin's disease other than paragranuloma, progressively transformed germinal centers also could be found in sequential biopsies of Hodgkin's disease of mixed and nodular sclerosis type. In one case, progressively transformed germinal centers preceded, in another case they occurred simultaneously in mixed type of Hodgkin's disease, and in two cases of nodular sclerosis type progressively transformed germinal centers developed after the onset of Hodgkin's disease. These findings suggest that progressively transformed germinal centers may be a result of different processes that may be occasionally related not only to nodular paragranuloma, but also in rare cases to nodular sclerosis and mixed type of Hodgkin's disease.     

The CTLA-4 gene is expressed in placental fibroblasts

In order to elucidate the mechanisms that ensure survival of the allogeneic fetus, we are investigating the expression pattern of genes that are involved in peripheral self-tolerance in tissues at the maternal-fetal interface. Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is a negative regulator of T cell activation and may modulate peripheral self-tolerance. Previously, we reported the preferential transmission of maternally-inherited shorter alleles at a 3'-UTR microsatellite locus to liveborn children, but random transmission of paternally-inherited alleles, suggesting that CTLA-4 may be involved in the maintenance of tolerance at the maternal-fetal interface. In this report, we demonstrate that CTLA-4 mRNA and protein are indeed expressed in fetal tissues at the maternal-fetal interface throughout gestation.     

Chronic cutaneous graft-versus-host disease in man.

This clinicopathologic study of patients with chronic graft-versus-host disease (GVHD) after allogeneic marrow transplantation emphasizes the most prominent feature of the syndrome, the cutaneous aspects, and describes the ophthalmic-oral sicca syndrome with sialoadenitis and the neurologic findings. Chronic cutaneous GVHD affected 19 of 92 recipients surviving 150 days or more. In 6 patients chronic GVHD presented as a continuation of acute GVHD; in 8 it occurred after the resolution of acute GVHD; and in 5 it arose without preceding acute GVHD, ie, de novo late onset. Two cutaneous types were distinguished. The generalized type affected 16 patients and ran a progressive course resulting in late complications of poikiloderma, diffuse dermal and subcutaneous fibrosis, and contractures. Microscopically, it resembled generalized morphea and lupus erythermatosus hypertrophicus et profundus. The local type affected 3 patients with a more variable picture of poikiloderma, dermal sclerosis, and contractures. Microscopically, it resembled lupus of erythematosus profundus and scleroderma. Guidelines for defining and subclassifying chronic cutaneous GVHD are proposed.     

Endothelial-cell injury in cutaneous acute graft-versus-host disease.

The presence of an erythematous skin rash and hemorrhagic complications in acute graft-versus-host disease (GVHD) suggest that the vasculature may be involved in the immunopathologic process. We reviewed endothelial and vascular histopathologic changes on light microscopy and on immunoperoxidase stained sections of skin biopsies obtained from 41 HLA-identical allogeneic marrow transplant recipients with at least grade 2 GVHD. Biopsies taken from 14 allogeneic HLA-identical bone marrow transplant recipients who never developed GVHD were used as controls. Sections were evaluated for evidence of immunologic vascular injury using the rank file analysis of histologic features, expression of HLA-DR antigen, and the distribution of fibrin and factor VIII-related antigen (F VIII RAg). Patients with acute GVHD had significantly greater intimal lymphocytic infiltrates, perivascular nuclear dust deposition, perivascular F VIII Rag extravasation and deposition and vascular proliferation than controls. We find significantly greater endothelial injury in GVHD patients, which may represent primary immunologic injury to the vasculature. The clinical findings in acute GVHD probably result from cumulative endothelial as well as epithelial injury.     

CTLA-4 and T cell activation.

The past year has seen significant advances in our understanding of the role of cytotoxic T lymphocyte antigen 4 (CTLA-4) in regulating T cell activation and tolerance. Recent studies indicate that CTLA-4 not only counterbalances CD28 signals but also can inhibit T cell responses independently of CD28. Recent work has also revealed a role for CTLA-4 in regulating Th1/Th2 differentiation. Manipulation of CTLA-4 in animal models of autoimmunity has shown that CTLA-4 regulates both the initiation and the progression of autoimmune diseases.     

CD137 is expressed by follicular dendritic cells and costimulates B lymphocyte activation in germinal centers

CD137, a member of the TNF receptor family, and its ligand are expressed on T lymphocytes and antigen-presenting cells (APC), respectively. During interaction with APC, T lymphocytes receive a potent, costimulatory signal through CD137. Reverse signaling has been demonstrated for the CD137 ligand, which causes activation in monocytes. Here we show that B lymphocytes also receive costimulatory signals through the CD137 ligand. Immobilized CD137 augmented proliferation of preactivated B lymphocytes up to fivefold and immunoglobulin synthesis, up to threefold. CD137 had no effect on resting cells. Further, we show that CD137 is expressed in vivo by follicular dendritic cells (FDC) in germinal centers. Germinal centers form during humoral immune responses and are essential for B lymphocyte affinity maturation. These data imply that, similar to the CD40 receptor/ligand system, which mediates T lymphocyte help to B lymphocytes after the first antigen encounter, the CD137 receptor/ligand system may mediate costimulation of B lymphocytes by FDC during affinity maturation.     

Subpopulations of B lymphocytes in germinal centers, II. A germinal center B cell subpopulation expresses sIgD and CD23

To understand B cell development in germinal centers, it is important to delineate the expression of surface antigens among germinal center cells. Because it is unclear whether germinal center cells express common antigens such as sIgD and CD23, we studied their expression among tonsillar lymphocytes with flow cytometry, immunohistochemistry, and in vitro stimulation. Upon studying a large number of tonsils with flow cytometry, we found that occasional tonsils have a very large number of sIgD+ cells among their PNA+ cells. Furthermore, the occasional tonsils with a large number of sIgD+ and PNA+ cells also have many CD23+ cells among their PNA+ cells. Tonsil sections stained immunohistochemically revealed germinal centers containing sIgD+ cells. In addition, PNA- and sIgD+ cells can be induced to express PNA binding sites in vitro without losing the expression of sIgD. Taking these findings together, we conclude that a subpopulation of germinal center B cells coexpresses sIgD and CD23.     

PRELI, the human homologue of the avian px19, is expressed by germinal center B lymphocytes

We report the identification of a human cDNA encoding a 25 kDa protein of relevant evolutionary and lymphoid interest (PRELI). PRELI was cloned by screening a B lymphocyte-specific cDNA library with a probe generated by mRNA differential display. PRELI amino acid sequence is 85% similar to the avian px19 protein, expressed within the blood islands and in the liver during avian embryo development. PRELI and px19 contain tandem repeats (A/TAEKAK) of the late embryogenesis abundant (LEA) motif, characteristic of a group of survival molecules and originally thought to be present only in plant proteins. Interestingly, PRELI expression is high in the fetal liver, a major site for B cell lymphopoiesis, while the mRNA levels in other fetal tissues such as the brain, lung, and kidney are comparatively low. At the adult stage, PRELI expression is drastically reduced in the liver but exhibits high mRNA levels in the spleen, brain, lung and kidney tissues, suggesting that PRELI expression may be important for the development of vital and immunocompetent organs. Moreover, PRELI is also highly expressed in the adult lymph nodes and peripheral blood leukocytes, further stressing that at the adult stage, PRELI expression may be important during secondary immune responses. Consistent with this hypothesis, the expression of PRELI is predominant within germinal centers (GC), a stage in which B lymphocytes are under a stressful selection pressure. Taken together these data: (i) strongly support the notion that the conserved LEA motif represents a phylogenetic link between plants and animals, (ii) reveal a novel molecule whose expression may play a role in the maturation of distinct human tissues, and (iii) suggest that PRELI expression may be important for GC B lymphocytes.     

CD40 ligand is constitutively expressed in a subset of T cell lymphomas and on the microenvironmental reactive T cells of follicular lymphomas and Hodgkin's disease.

Although CD40 has been extensively studied in B- and T-cell non-Hodgkin's lymphomas (NHLs)/leukemias, and more recently in Hodgkin's disease (HD), little is known about the expression of its ligand (CD40L) in lymphoproliferative disorders other than T-cell NHLs/leukemias. A series of 121 lymphoma/leukemia samples, including 35 cases of HD, 34 T-cell and 39 B-cells NHLs, 2 cases of adult T-cell leukemia/lymphoma, and 11 cases of T-cell acute lymphoblastic leukemia, were evaluated for CD40L expression by immunostaining of frozen tissue sections and flow cytometry with the anti-CD40L monoclonal antibody M90. CD40L was constitutively expressed by neoplastic cells in 15 of 36 (42%) T-cell NHLs/adult T-cell leukemia/lymphomas, almost invariably those displaying the CD4+/CD8- phenotype, whereas no CD40L-expressing tumor cells could be found in B-cell NHL and HD. Among T-cell acute lymphoblastic leukemias, CD40L was detected only on 2 cases displaying a stem-cell-like phenotype. In follicular B-cell lymphomas a large number of CD40L-expressing CD3+/CD4+ T lymphocytes were found admixed with tumor cells within the neoplastic follicles and in their surrounding areas. In the nonfollicular B-cell lymphomas, CD40L-positive CD3+/CD4+ T lymphocytes were few or absent. In all HD subtypes other than the nodular lymphocytic predominance, CD40L-expressing CD3+/CD4+ T lymphocytes were numerous in the HD-involved areas and were mainly located in close proximity to the Reed-Sternberg cells. Our data indicate that in human lymphomas CD40L is preferentially expressed by a restricted subset of T-cell lymphomas, mostly with CD4 immunophenotype. Finally, we have provided morphological evidence that CD40L may play an important role in the cell contact-dependent interaction of tumor B-cells (CD40+) within the neoplastic follicles or Reed-Sternberg cells (CD40+) in HD-involved areas and the microenvironmental CD3+/CD4+/CD40L+ T lymphocytes.     

Interaction between serum factors and T lymphocytes in Hodgkin's disease. Use as a diagnostic test.

We studied the mechanism of defective binding of sheep erythrocytes to the surface of peripheral blood T lymphocytes (E-rosette-formation) in Hodgkin's disease. The decreased percentage of E-rosette-forming cells (range, 21 to 77 per cent) in 25 patients with Hodgkin's disease was reversed and returned to normal range (52 to 78 per cent) by prior incubation of the T lymphocytes in tissue-culture medium with 20 per cent fetal-calf serum for 18 to 24 hours. The percentage of E-rosette-forming cells was suppressed by additional incubation with serum from patients with Hodgkin's disease (range, 20 to 61 per cent) but not with serum from patients with other neoplasms or from normal subjects (range, 52 to 74 per cent). Only target T lymphocytes from patients with Hodgkin's disease were suppressed by Hodgkin-disease serum. The findings suggest that there is a specific interaction between serum factors and the surface of peripheral blood T lymphocytes in Hodgkin's disease.     

Cytogenetic findings in nodular paragranuloma (Hodgkin's disease with lymphocytic predominance; nodular) and in progressively transformed germinal centers

Cytogenetic studies were performed in a case of progressively transformed germinal centers (PTGC), and in a case of nodular paragranuloma (NP; Hodgkin's disease with lymphocytic predominance, nodular type). No cytogenetic abnormalities were detected in PTGC. Chromosomal aberrations (hyperdiploidy, 6q-, +21, and several unidentified markers) were found in NP. The results support the proposal that PTGC are reactive in nature and NP is a neoplasm. Chromosomal analysis could provide practical diagnostic aids in the differential diagnosis of PTGC and NP.     

Increased expression of CTLA-4 (CD152) by T and B lymphocytes in Wegener's granulomatosis.

CTLA-4 (CD152) is a surface molecule of activated T cells with sequence homology to CD28. Both molecules bind to the same ligands, B7.1 (CD80) and B7.2 (CD86) but have antagonistic functions. While CD28 is an important costimulator, CTLA-4 has an essential inhibitory function in maintaining the homeostasis of the immune system. Furthermore, CTLA-4 has a role in inducing a Th1 response and suppressing Th2 cytokines, an effect which is antagonized by CD28. Many autoimmune diseases are characterized by an overwhelming production of Th1 cytokines. Recently, the predominance of the Th1 cytokine pattern has been directly observed in the granulomatous inflammation of patients with Wegener's granulomatosis. The balance between CD28 and CTLA-4 expression by T lymphocytes could be a factor in the pathogenesis of autoimmune diseases. Down regulation of CD28 predominantly on CD8+ T cells has been described in Wegner's granulomatosis; however, analysis of CTLA-4 is complicated by its low expression levels. Here we have used potent signal enhancement to study CTLA-4 on PBMC in patients with Wegener's granulomatosis (n = 25) in comparison with healthy controls (n = 19). Expression levels of CTLA-4 were significantly increased selectively on CD4+ and possibly also on CD4-/CD8- T cells in Wegener's granulomatosis. High CTLA-4 expression by T lymphocytes was associated with more severe disease. In contrast, after stimulation with the mitogen PHA, CTLA-4 levels were strongly increased on T cells from controls but in T cells from Wegener's granulomatosis patients this response was severely impaired. Interestingly, while CTLA-4 was seen exclusively on T cells in control individuals, about half of the Wegener's patients showed CTLA-4 expression by a fraction of peripheral B lymphocytes. CTLA-4 positive B cells in the periphery were associated with less acute disease.     

Bu-2, a novel avian cell surface antigen on B cells and a population of non-lymphoid cells, is expressed homogeneously in germinal centers

A monoclonal antibody (mAb), Hy30, was generated against bursal cells. Under reducing conditions, it immunoprecipitates a cell surface antigen with an apparent molecular weight of 66 kD that is distinct from immunoglobulin and MHC class II. The antigen recognized by Hy30 is found on greater than 95% of all bursal cells, on a population of thymus resident cells, and on blood, spleen, and marrow mononuclear cells. Immunohistological analysis of tissue sections revealed that the majority of the staining by Hy30 occurs in the B cell areas of the spleen and thymus. Flow cytometric analysis demonstrated that the antigen recognized by Hy30 is found on both immunoglobulin positive (Ig+) and negative (Ig-) cells. Analysis of a chicken rendered B cell deficient by treatment with cyclophosphamide at hatch confirmed this observation. In these birds, the medullary dendritic cells of the bursa and Ig- cells of the "B-cell areas" of the spleen and thymus expressed the Hy30 Ag. Analysis of several avian tumor lines did not suggest an obvious lineage for these Hy30+ Ig- cells. However, analysis of germinal centers suggested that these cells may be tissue macrophages or dendritic cells. This is consistent with previously reported histology of these "B-cell areas". Flow cytometric analysis of the antigen recognized by Hy30 demonstrates that it is distinct from the Bu-1 B-cell surface antigen and we designate it as Bu-2.     

Association between IgG4-related disease and progressively transformed germinal centers of lymph nodes

Progressively transformed germinal centers is a benign condition of unknown pathogenesis characterized by a distinctive variant form of reactive follicular hyperplasia in lymph nodes. We recently reported Ig G4-related disease in progressively transformed germinal centers. However, no large case series has been reported and clinicopathologic findings remain unclear. Here, we report 40 Japanese patients (28 men, 12 women; median age, 56 years) with progressively transformed germinal centers of the lymph nodes who fulfilled the histological diagnostic criteria for IgG4-related disease (IgG4(+) progressively transformed germinal centers), with asymptomatic localized lymphadenopathy involving the submandibular nodes in 24, submandibular and cervical nodes in 14, cervical nodes only in 1, and cervical and supraclavicular nodes in 1. In all, 16 (52%) of 31 examined patients had allergic disease. Histologically, the lymph nodes demonstrated uniform histological findings, namely marked follicular hyperplasia with progressively transformed germinal centers, and localization of the majority of IgG4(+) plasma cells in the germinal centers. Serum IgG4, serum IgE and peripheral blood eosinophils were elevated in 87%, 92% and 53% of examined patients, respectively. Eighteen patients subsequently developed extranodal lesions (including five who developed systemic disease), which on histological examination were consistent with IgG4-related disease. IgG4(+) progressively transformed germinal centers presents with uniform clinicopathological features of asymptomatic localized submandibular lymphadenopathy, which persists and/or relapses, and sometimes progresses to extranodal lesions or systemic disease. Nine patients were administered steroid therapy when the lesions progressed, to which all responded well. We suggest that IgG4(+) progressively transformed germinal centers should be included in the IgG4-related disease spectrum.