Differential expression of the HECA-452 antigen (cutaneous lymphocyte associated antigen, CLA) in cutaneous and non-cutaneous T-cell lymphomas

The monoclonal antibody HECA-452 identifies an antigen that is primarily expressed on high endothelial venules, the preferred site of lymphocyte extravasation in lymphoid tissues, and also on a subpopulation of myelomonocytic cells and some T-cells. We investigated the expression of the HECA-452 antigen, also called the cutaneous lymphocyte associated antigen, in primary cutaneous and primary non-cutaneous T-cell non-Hodgkin's lymphomas. The tumour cells of cutaneous T-cell non-Hodgkin's lymphomas were positive in 53% of cases, while only 5% of the non-cutaneous lymphomas were positive. These differences were also present in morphologically identical tumours. Thus, the tumour cells in six out of 10 primary cutaneous anaplastic large cell T-cell lymphomas were positive, while they were positive in none of 24 primary non-cutaneous anaplastic large cell T-cell lymphomas. In general, primary cutaneous and primary nasal T-cell non-Hodgkin's lymphomas were devoid of HECA-452 positive high endothelial venules, whereas most nodal T-cell non-Hodgkin's lymphomas contained HECA-452 positive high endothelial venules. These observations suggest that the HECA-452 antigen might be related to a skin-associated type of lymphoid tissue and to lymphomas originating in the skin. However, the results of HECA-452 expression in secondary sites, and the clinical data of the primary cutaneous large cell lymphomas did not support the concept that HECA-452 is functionally involved in homing to the skin, or that loss of the HECA-452 antigen is related to tumour progression of primary cutaneous T-cell lymphomas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Function of CD44(Pgp-1) homing receptor in human T cell precursors

T cell precursors migrate from extrathymic hematopoietic tissues and differentiate after encountering the thymic microenvironment. We asked whether human T cell precursors express the CD44(Pgp-1/gp90HR) class of homing receptors that have been implicated in the traffic of hematopoietic cells, such as lymphocyte entry to peripheral lymphoid organs. Flow cytometry and immunoprecipitation studies demonstrate that CD7+34+, CD1-2-3-4-8-14-16-20- cells in bone marrow and thymus, which have been shown to exhibit features of T cell precursors, bear CD44. Immunohistological studies show that clusters of thymocytes in the subcapsular and the inner cortex and most medullary thymocytes are clearly CD44+, whereas the expression of CD44 is selectively downregulated in CD3- and CD3low functionally incompetent cortical thymocytes. The expression of CD44 is not restricted to T cell precursors but also occurs in thymic stroma, which bear a different molecular species of CD44. CD44-specific antibodies exert stimulatory effects on T cell precursors, a process that is dependent on stromal cells. We postulate that CD44 might be an adhesion molecule for precursor homing to thymus and that it participates in cell-to-cell interactions within the thymic environment.     

Intrathymic ontogeny of the T cell receptor associated CD3 (T3) antigen

Intrathymic T cell maturation has been studied in great detail, yet much of this process remains controversial. One of the critical steps in thymocyte maturation is the surface expression of the T cell antigen receptor associated CD3 (T3) antigen. The expression and ultrastructural localization of this antigen was therefore studied in tissue sections of five human thymuses using the monoclonal antibody UCHT-1. Thymocytes were also independently categorized morphologically as small nonblastic, large blastic, or intermediate. CD3 positivity was identified in 89% of cortical thymocytes and 92% of medullary thymocytes. Of the CD3+ cells, staining was present in the perinuclear region in 48% of cortical thymocytes and in only 11% of medullary thymocytes. Surface membrane staining was present in 87% of CD3+ cortical thymocytes and 99% of CD3+ medullary thymocytes. Of the CD3+ cortical large blastic thymocytes, 97% had perinuclear staining, but only 31% had surface positivity. Conversely, 98% of CD3+ medullary large blastic thymocytes had surface staining, but only 17% had perinuclear positivity. Almost all cortical and medullary small nonblastic thymocytes had surface membrane CD3 positivity, whereas perinuclear positivity was rare in these cells. These data suggest that the most immature CD3+ thymocytes (the large blasts with perinuclear CD3 positivity only) are present almost exclusively in the cortex. Maturation defined by the loss of perinuclear CD3 positivity and the acquisition of surface CD3 also occurs in the cortex. The vast majority of medullary thymocytes have surface CD3 positivity only.     

Human antigen-specific memory T cells express the homing receptor (LAM-1) necessary for lymphocyte recirculation.

Lymphocytes must circulate from blood into lymphoid tissues and sites of infection and inflammation to function efficiently in vivo. This process of "homing" is in part directed by the expression of the leukocyte adhesion molecule (LAM-1, also known as TQ1 and Leu-8) in humans and the homologous MEL-14 antigen in mice. In this report, we demonstrate that the LAM-1 molecule is a 74-kDa protein and that only half of the CD4+ T cells in humans which have a memory phenotype (CD45RA -CD29hi) express the LAM-1 molecule. Functionally, these two phenotypically distinct subpopulations of memory cells were quite different. The LAM-1+ memory cells proliferated better to recall antigen and induced three to seven times higher levels of B cell immunoglobulin secretion than their LAM-1- counterparts. Thus, antigen-specific memory T cells within the helper lineage express the homing receptor appropriate for regulating their migration to secondary lymphoid tissues and sites of inflammation.     

Functional evidence that the HECA-452 antigen is involved in the adhesion of human neutrophils and lymphocytes to tumour necrosis factor-alpha-stimulated endothelial cells.

The migration of leucocytes into tissues is a process mediated by leucocyte endothelial interactions, in which adhesion receptors play a crucial role. Recently, it was found that 80-90% of T cells in inflammatory skin diseases were reactive to the monoclonal antibody (mAb) HECA-452+ in contrast to inflamed non-cutaneous tissues. It was suggested that the HECA-452 antigen is a homing receptor for lymphocyte migration into skin. This receptor was designated cutaneous lymphocyte-associated antigen or CLA and subsequently identified as a group of related sugar moieties. E-selectin, formerly known as ELAM-1 expressed by the endothelium has been implicated to be a counter-receptor for CLA. In this study, we investigated the adhesion of HECA-452+ leucocytes, i.e. freshly isolated neutrophils and B-cell line BV173 to tumour necrosis factor-alpha (TNF-alpha)-stimulated (E-selectin+) endothelial cells. We found that the adhesion of these cells could be inhibited significantly by mAb HECA-452, in a similar fashion to CSLEX1, a mAb specific for E-selectin ligand sialyl Lewisx. This inhibiting effect of both mAb on the adhesion of polymorphonuclear leucocytes (PMN) and BV173 could only be demonstrated when the assay was performed at 4 degrees, but not at 37 degrees. Furthermore, using immunohistochemical analysis we found that the mAb HECA-452-reactive epitope is different from that recognized by CSLEX1. The present results give direct evidence that the antigen recognized by HECA-452 is involved in the adhesion of leucocytes to endothelial cells, although this antigenic epitope is different from that reactive to CSLEX1.     

The human peripheral lymph node vascular addressin. An inducible endothelial antigen involved in lymphocyte homing.

The extravasation of blood-borne lymphocytes into organized lymphoid tissues and sites of chronic inflammation is directed in part by interactions of lymphocyte surface adhesion molecules, known as homing receptors, with tissue-selective endothelial ligands called vascular addressins. In mice and humans, lymphocyte L-selectin and the peripheral lymph node addressin (PNAd) form a homing receptor-endothelial ligand pair involved in lymphocyte traffic to peripheral lymph node (PLN). We have examined the tissue distribution and function of human PNAd, using monoclonal antibody MECA-79 and in vitro assays of L-selectin-dependent lymphocyte binding. We demonstrate that PNAd is expressed by human high endothelial venules (HEV) in lymphoid tissues which support lymphocyte adhesion via a PLN-associated recognition system. MECA-79 inhibits adhesion to these HEV of a cell line that binds predominantly via the PLN-homing receptor, L-selectin, but has no effect on adhesion by a mucosal HEV-binding cell line. Furthermore, MECA-79 blocks binding of human peripheral blood mononuclear cells to both PLN and tonsil HEV, but not significantly to HEV in the appendix. In addition, we demonstrate PNAd induction on venules at chronic inflammatory sites in humans, particularly sites with severe or long-standing chronic inflammatory involvement. These results confirm that PNAd functions as a PLN vascular addressin in humans, and that in addition to directing normal lymphocyte recirculation to lymph nodes and tonsils, this addressin likely participates in lymphocyte recruitment to sites of chronic inflammation.     

Class II (DR) antigen expression on CD8+ lymphocyte subsets in acquired immune deficiency syndrome (AIDS)

In a selected group of human immunodeficiency virus (HIV)-infected patients we confirm the expansion of a CD8⁺ T-lymphocyte subset, i.e., the CD8⁺/Leu7⁺ cells, which account for 30% of the lymphocytes, compared to 3% in the control donors. In addition, a CD8⁺ T-lymphocyte subset that coexpresses class II (DR) antigens, i.e., CD8⁺/DR⁺ cells, is also increased from 1.5% in controls to 27% in the HIV-infected patients. Using three-color immunofluorescence and flow cytometry we can demonstrate that the CD8⁺/Leu7⁺ and the CD8⁺/class II⁺ cells are not distinct but overlapping subsets. In the HIV-infected patients 42% of the CD8⁺/Leu7⁺ cells were strongly positive for class II and these CD8⁺/Leu7⁺/class II⁺ cells accounted for 13% of all lymphocytes. These findings indicate that the expanded CD8⁺/Leu7⁺ cells are activated and hence might be actively involved in immune defense in acquired immune deficiency syndrome (AIDS).     

Expression of CD44 molecules and CD44 ligands during human thymic fetal development: expression of CD44 isoforms is developmentally regulated

It has recently been recognized that CD44 comprises a largefamily of alternatively spliced forms.In the thymus, CD44 hasbeen postulated to play an important role in immature T cellmigration and maturation. In this paper, we have studied theexpression of CD44 molecules and two CD44 ligands, hyaluronan(HA) and fibronectin (FN), during human thymic fetal development.We found that mAbs against all CD44 isoforms (A3D8 or A1G3)reacted with both thymic epithelial (TE) cells and thymocytesbeginning at the time of initial colonization of the human thymusby hematopoietic stem cells at 8.2 weeks of fetal gestation.However, mAbs specific for splice variants of CD44 containingmembrane-proximal inserts (11.24, 11.10 and 11.9) reacted onlywith terminally differentiated TE cells in and around Hassall'sbodies beginning at 16–19 weeks of fetal gestation. Studiesof differentiated versus undifferentiated TE cells in vitroconfirmed the selective expression of CD44 variant isoformson terminally differentiated TE cells. Expression of HA andFN was determined by fluorescence microscopy using either biotlnylated-HAbinding protein or an anti-FN mAb. We found that whereas FNwas present throughout the human fetal thymus beginning at 8.2weeks, HA was not present until 16 weeks of gestational age.These data demonstrate the differential expression of standardversus variant CD44 isoforms during thymic ontogeny and implicateCD44 interactions with ligands other than HA as important inthe earlier stages of humanthymus development     

Non-random recirculation of small, CD4+ and CD8+ T lymphocytes in sheep: evidence for lymphocyte subset-specific lymphocyte- endothelial cell recognition

The migratory properties of small, CD4+ and CD8+ T lymphocyte subsets have been examined in sheep under physiological conditions. Lymphocytes obtained free-floating in lymph were directly labeled with fluorochrome in vitro and returned to the blood of the same animal. Over the next 48 h the lymph collection bottles were replaced at various times. The cells in these collections, as well as an aliquot of the cells used for direct fluorescent labeling, were then phenotyped with monoclonal antibodies (mAbs) which define the mutually exclusive CD4+ and CD8+ T lymphocyte subsets in sheep. Binding of mAbs was detected by using secondary reagents labeled with a fluorochrome of a different colour. All cell samples were analyzed by flow cytometry and CD4/CD8 ratios were determined for the recirculated, fluorochrome-labeled population in each lymph collection. The mean CD4/CD8 ratio was then calculated and compared with the CD4/CD8 ratio of the intravenously infused starting population. In three experiments employing efferent prescapular lymph cells, three experiments employing efferent intestinal lymph cells and two experiments employing afferent intestinal lymph cells, the mean CD4/CD8 ratio of the recirculated, fluorochrome-labeled population was different from the CD4/CD8 ratio of the starting population, thereby indicating that non-random migration of these subsets had occurred. The finding that the CD4/CD8 ratio of the recirculated population was higher than the CD4/CD8 ratio of the transfused starting population in every case provides strong experimental support for the hypothesis that small, CD4+ T cells are extracted from the blood by specialized vascular endothelium with greater efficiency than small, CD8+ T cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

The human hematopoietic progenitor cell antigen (CD34) in vascular neoplasia.

The human hematopoietic progenitor cell antigen CD34 is synthesized and expressed by early normal hematopoietic progenitor cells and by many acute leukemias. Anti-CD34 antibodies also have been reported to stain blood vessels in tissue sections, and, more recently, CD34 mRNA has been detected in vascular endothelial cells. Therefore, the authors studied the diagnostic utility of immunohistochemical CD34 antigen detection in tumors of endothelial cell derivation and compared the results with stains for von Willebrand (vW) factor. A wide variety of epithelial and mesenchymal neoplasms also were examined to assess the specificity of CD34 for vascular neoplasia. Seven cases of angiosarcoma (seven of seven), five cases of Kaposi's sarcoma (five of five), and eight cases of epithelioid hemangioendothelioma (eight of eight) were moderately to strongly positive for CD34. This reactivity was equally intense in frozen sections, alcohol-fixed tissue, and formalin-fixed specimens. In many cases, the malignant endothelial cells stained more strongly than adjacent benign endothelium. Moreover, in most cases CD34 positivity was quantitatively and qualitatively stronger than staining for vW factor. Two cases of hemangiopericytoma (two of two) were CD34 positive but stained less intensely than the angiosarcomas, Kaposi's sarcomas, or hemangioendotheliomas. Five of six cases of hemangioma also stained positively for CD34; the nonreactive tumor in this group was the only one among 28 vascular neoplasms studied that was not reactive for CD34. In comparison, 9 of the 28 vascular tumors did not stain for vW factor. Three hundred fifty-seven tumors of nonvascular derivation also were examined for CD34 antigen expression. Focal light staining was seen in one pulmonary squamous cell carcinoma; moderate to intense staining was observed in half of the epithelioid sarcomas studied (8 of 16) and in a minority of leiomyosarcomas (3 of 22). These findings indicate that CD34 is a sensitive and relatively specific marker for neoplasms of vascular origin.     

Route of lymphocyte migration through the high endothelial venule (HEV) in human palatine tonsil

Eleven palatine tonsils were collected from subjects who underwent tonsillectomy in Christian Medical College Hospital and the route of migration of lymphocytes through the high endothelial vessel was studied under EM. In the interendothelial route, migration of a lymphocyte through HEV wall began with the adhesion of a lymphocyte to the surface of endothelial cells by means of a short cytoplasmic projection in the vicinity of intercellular space. The projection extended into the cleft between adjacent endothelial cells. The lymphocyte migrated through HEV by diapedesis. After the lymphocyte had traversed the interendothelial space, it occupied the subendothelial space. In the transendothelial route, migration of a lymphocyte through HEV was initiated by adherence of the lymphocyte to the endothelial cell. The adherent lymphocyte compressed or invaginated into the cytoplasm of the endothelial cell, entered the endothelial cell, was completely enclosed within the endothelial cell cytoplasm, and emerged from the endothelial cell to occupy the subendothelial space. Evidence is presented from static transmission electron microscopic pictures for the migration of lymphocytes by both interendothelial and transendothelial routes through the high endothelial venule.     

Defective B cell ontogeny and immune response in human complement receptor 2 (CR2, CD21) transgenic mice is partially recovered in the absence of C3

Mice prematurely expressing human CR2 (hCR2) in the B cell lineage have a defective B cell ontogeny and immune response. Our recent analysis of this phenotype suggested that signaling through hCR2 and presumably mouse CD19 on the B cell surface, during bone marrow development, could result in the observed changes in B cell function in these mice. To test this hypothesis, we back crossed hCR2(high) transgenic mice onto the CD19(-/-) background. CD19(-/-)hCR2(high) mice were found to possess even fewer mature B cells than their CD19(+/+)hCR2(high) littermates, demonstrating that loss of CD19 exacerbated the effects elicited through hCR2. This data suggests that CD19 provides a survival signal during B cell development in this model. Next, we examined if the removal of the main ligand for CR2, namely C3d, through back-crossing onto the C3(-/-) background could restore normal B cell development. However, we found only minor recovery in peripheral B cell numbers and no obvious change in function. This was despite a three-fold increase in the level of hCR2 expression on B cells isolated from the spleen or bone marrow of C3(-/-)hCR2(high) mice when compared with C3 sufficient littermates. These data demonstrate that hCR2 is integrated in mouse B cell signaling and that the downstream effects of hCR2 expression during early B cell development are partially but not completely due to interaction with C3 fragments and signaling through CD19 in the bone marrow environment.     

The murine homologue of the T lymphocyte CD2 antigen: molecular cloning, chromosome assignment and cell surface expression

The human T lymphocyte antigen CD2 (T11, sheep erythrocyte receptor) is expressed on all peripheral T cells and all but the most immature thymocytes. Experiments with monoclonal antibodies against CD2 suggest that CD2 is the cell surface receptor for a natural ligand involved in T cell proliferation. Clarification of the functional role of CD2 would be facilitated by the identification of CD2 in the mouse. However, antibodies that recognize the murine homologue have not been described. An alternative approach to the identification of the murine homologue was to use cross-species DNA hybridization, employing human CD2 cDNA as a probe. Clones encoding the murine homologue were isolated from a murine T helper cell cDNA library. The murine cDNA sequence encoded a predicted mature polypeptide of 322 amino acids that showed 54% identity with the predicted human sequence. As with the human polypeptide, the cytoplasmic domain was large, and rich in proline and basic residues. CD2 mRNA was expressed in murine thymus and spleen, and in the T cell line EL4. The murine CD2 gene was assigned to chromosome 3 by Southern blot analysis of mouse-hamster somatic cell hybrids. A rabbit antiserum raised against purified human CD2, precipitated from surface-labeled mouse thymocytes a glycoprotein of Mr 55,000-66,000 which decreased to Mr 35,000 on digestion with endo-beta-acetylglucosaminidase F. These sizes are consistent with those predicted for the murine CD2 antigen from the cDNA sequence.     

Spatiotemporal expression gradients of the carbohydrate antigen (CD15) (Lewis X) during development of the human basal ganglia.

The developmental expression pattern of the carbohydrate epitope CD15 (Lewis X, Le X) (alpha1-->3-fucosyl-N-acetyl-lactosamine) has been immunocytochemically evaluated in paraffin sections within the human basal ganglia from 10 weeks gestation to three years after birth. At 11 weeks of gestation, CD15 (Le X) positive radial glial cells were located in the anterior and dorsal parts of the lateral ganglionic eminence. Their processes ran from the subventricular zone radially in a highly ordered fashion to the dorsolateral margin of the caudate nucleus and further to the lateral rim of the putamen. At 12 weeks of gestation, strands of CD15 (Le X) material continued to the pial surface, forming a continuous CD15 (Le X) positive borderline separating the accumbens nucleus and olfactory tubercle from the piriform cortex. At 13 weeks of gestation the dorsal putamen was completely CD15 (Le X) immunoreactive along its perimeter and CD15 (Le X) patches, consisting of fine granular material, appeared at the dorsolateral margin of the putamen at this age; while the first CD15 (Le X) patches in the caudate nucleus were observed four weeks later. The matrix compartment of the caudate and dorsal putamen became gradually stained by granular CD15 (Le X) positive material into which CD15 (Le X) immunoreactive somata were embedded. The striking contrast in staining between patch and matrix compartments disappeared shortly after birth. The ventral striatum did not become immunoreactive until the last few weeks before birth. After the formation of CD15 (Le X) positive patches in the striatum (from 12 weeks of gestation), delicate CD15 (Le X) fibres, often accumulated in bundles and related to the striatal patches, became apparent coursing towards the external pallidal lamina and the globus pallidus. Immunoreactivity in the globus pallidus itself was transient, emerging from 16 weeks of gestation, reaching a peak at 21 weeks of gestation and disappearing by birth. Both processes, i.e. the occurrence of CD15 (Le X) striatopallidal fibres and the emerging immunoreactivity in their pallidal target, may be interrelated, so that ingrowing CD15 (Le X) positive axons from the striatum provoke CD15 (Le X) expression in the external and internal pallidum. The variable patterns and intensities of CD15 (Le X) expression are possibly related to periods of maturation of the striatum and the establishment of functional interactions within the basal ganglia. Differential staining of patch and matrix in the developing neostriatum suggests that a distinct phase of cellular adhesion or dishesion mediated by the CD15 (Le X) epitope occurs during establishment of the patch and matrix regions.     

Cross-linking of the T cell receptor complex with the subset-specific differentiation antigen stimulates interleukin 2 receptor expression in human CD4 and CD8 T cells

Nonpolymorphic interactions between the T cell differentiation antigens CD4 or CD8 and major histocompatibility complex (MHC)-encoded molecules have been postulated to participate in antigen recognition of MHC-restricted T cells. This would imply simultaneous binding of CD4/8 and of the T cell receptor complex (Ti/CD3) to MHC molecules on the stimulator or target cell. In this report experimental evidence is provided that simultaneous binding by antibodies of Ti/CD3 and of CD4 or CD8 leads to the expression of interleukin 2 (IL 2) receptors in resting human T cells and to their subsequent proliferation in the presence of recombinant IL 2 (rIL 2). This could be shown by using a novel anti-CD3 monoclonal antibody (BMA 030) which alone only marginally stimulates highly purified human T cells even when applied in cross-linked form. However, human T cell subpopulations could be stimulated to grow in the presence of rIL 2 when BMA 030 was fixed to a solid support in combination with antibodies to either CD4 or CD8. In limiting dilution experiments, the frequencies of CD4 and CD8 T cells activated by the antibody combinations were similar to those activated by phytohemagglutinin in the presence of irradiated adherent cells. No stimulation was achieved if both or one antibody was applied in soluble form. In contrast, soluble antibodies inhibited activation by solid-phase antibodies. Taken together, cross-linking of Ti/CD3 with CD4/8 seems to be essential for T cell activation in cases of ligands that bind but do not activate T cells on their own--a situation that may reflect the interaction of T cell receptors with MHC-encoded molecules in association with antigen.     

Differential expression of lymphocyte homing receptors by human memory/effector T cells in pulmonary versus cutaneous immune effector sites

The heterogeneous expression of lymphocyte homing receptors (HR) by the (CD45RA^low/RO^high) memory/effector T cell population in the human is thought to define subsets with tissue-selective recirculatory potential. To investigate further the localization characteristics of these T cells, we used multiparameter flow cytometry to quantitate T cell subsets defined by expression of the skin-selective HR called the cutaneous lymphocyte-associated antigen (CLA), the peripheral lymph node (PLN) HR L-selectin, the mucosal-associated HR α4β7-integrin, and the mucosal-associated adhesion molecule αeβ7-integrin in either cutaneous or pulmonary immune effector sites and corresponding peripheral blood. Compared to peripheral blood, skin T cells were highly enriched for the CLA⁺/L-selectin⁺/αeβ7-integrin^? memory/effector subset, whereas lung memory/effector T cells were predominantly CLA^{?to low} L-selectin^?, and almost half were αeβ7-integrin⁺. α4β7-integrin expressing memory/effector T cells were diminished in both skin and lung, suggesting that this HR is not a major participant in determining localization specificity in either of these sites. The characteristic pulmonary T cell HR phenotype did not significantly differ between the normal subjects and those with pulmonary inflammatory disease, and did not correlate with markers of T cell activation. Induction of a rapid up-regulation of pulmonary inflammation via intrabronchial allergen challenge in asthmatic patients tended to decrease localization specificity, resulting in a more general importation of memory/effector subsets. Taken together, these results suggest that tissue microenvironments play a major role in determining the character of local T cell infiltrates via their ability to import and retain memory/effector subsets selectively or, more generally, depending on the intensity of local inflammatory stimuli.     

Fetal antigen 1 (FA1) in the human pancreas: cell type expression, topological and quantitative variations during development

Monospecific rabbit anti-human fetal antigen 1 (FA1), was used to examine the distribution of FA1 during the development of the human fetal pancreas and liver using an indirect immunoperoxidase technique. FA1 was expressed by 94% of the glandular epithelial cells of the branching ducts in the pancreatic anlage at week 7 of gestation. This pattern changed during the development of the human pancreas, 64% of the glandular cells being FA1 positive at week 17 of gestation, decreasing to 11% in the infant (4 months after birth). In the infant and adults the FA1 expression was restricted to a subpopulation of -cells within the islets of Langerhans. Insulin immunoreactive cells were scattered throughout the epithelium of primitive branching pancreatic ducts at week 7 of gestation, well before the formation of islets. From the 7th through to the 17th week of gestation, FA1 was found in the cytoplasm of fetal hepatocytes, whereas no staining was observed in the liver from a 4-month-old infant. No FA1 expression was found in the epithelium of the developing gut. The present findings indicate that the glandular epithelial cells in the developing pancreas may serve as stem cells, which, if appropriately induced, may differentiate into endocrine cells. Fetal antigen 1 (FA1) may take part in or be a result of this differentiation.     

Altered expression of the lymphocyte activation antigen CD30 in active celiac disease

Interleukin (IL)-15 and CD30 may be associated with the ongoing intestinal immunologic activation in celiac disease (CD). We studied duodenal biopsies and blood samples of patients with active CD (Cel) and controls in order to determine the regulatory role proposed for CD30⁺ T cells in this Th1-driven disease and the potential influences of IL-15 on CD30 expression. We detected that a CD30⁺ T-cell subpopulation persists longer in Cel after a 5 day incubation with anti-CD3 antibody than in controls (p = 0.0063). CD30 upregulation by IL-15 in T blasts was greater in Cel than in controls (p = 0.0062). At the mucosal compartment, the CD30 antigen was examined by immunohistochemistry and quantified on isolated lamina propria (LP) and epithelial T cells by flow cytometry. For Cel and controls, similar mean percentages of CD3⁺CD30⁺ intraepithelial T cells (5.88 vs. 5.51, p = ns) and LP T cells (7.38 vs. 7.49, p = ns) were observed at baseline and after in vitro gliadin challenge of duodenal biopsy samples. Our study demonstrates the occurrence of potentially important alterations of the immune response at the peripheral compartment. Our findings also allow us to speculate that a negative effect of soluble mediators at the mucosal compartment might counteract the latent influence of IL-15 on CD30 expression precluding a more severe course of active CD.     

The fatty acid composition of the lymphocyte cell membrane. Influence on interactions with high endothelium and the expression of homing receptors.

By incubating mouse lymphocytes in vitro with various fatty acids in an otherwise lipid-free medium, the lipid composition of the cell membrane was varied. These changes resulted in an altered adhesion pattern on High Endothelial Venules (HEV) using an in vitro adherence assay. Incubation with linoleic acid (18:2) resulted in an increased adherence of T and B lymphocytes, linolenic acid (18:3) had no influence and both arachidonic acid (20:4) and arachidic acid (20:0) resulted in a decreased adherence of the two cell types when the adherence assay was performed using HEV from peripheral lymph nodes. Using HEV from mucosa associated Peyer's patches, T and B cells incubated with arachidic acid or arachidonic acid were less able to adhere this type of HEV. After incubation with linoleic acid, T lymphocytes adhere better to the Peyer's patches HEV whereas B cells showed a decrease in adherence and linolenic acid resulted in a decreased adherence of only B lymphocytes. FACS analysis revealed that MEL-14 expression as well as the expression of LFA-1 was somewhat elevated in intensity on T and B lymphocytes after incubation with linoleic acid. In contrast, the intensity for MEL-14 had decreased after arachidic acid or arachidonic acid. In case of arachidic acid the LFA-1 expression had also decreased. No changes were found after incubation with linolenic acid. The results suggest a role for the lipid composition of the membrane in recirculation patterns of lymphocytes.