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Biomedical subjects

M Marazuela

Publications and source records attributed to M Marazuela.

At least 19 recordsLinked to original sources
PubMed2000

Phenotypic and functional characteristics of hematopoietic cell lineages in CD69-deficient mice.

AIM/CD69 is the earliest leukocyte activation antigen and is expressed mainly by activated T, B, and natural killer (NK) cells. It is also constitutively expressed by platelets, by bone marrow myeloid precursors, and by small subsets of resident lymphocytes in the secondary lymphoid tissues. The engagement of CD69 by specific antibodies induces intracellular signals, including Ca(++) flux, cytokine synthesis, and cell proliferation. To investigate the physiological relevance of CD69, we generated mice deficient in CD69 (CD69-/-) by gene targeting in embryonic stem cells. CD69 (-/-) mice showed largely normal hematopoietic cell development and normal T-cell subpopulations in thymus and periphery. Furthermore, studies of negative- and positive-thymocyte selection using a T-cell receptor transgenic model demonstrated that these processes were not altered in CD69 (-/-) mice. In addition, natural killer and cytotoxic T lymphocyte cells from CD69-deficient mice displayed cytotoxic activity similar to that of wild-type mice. Interestingly, B-cell development was affected in the absence of CD69. The B220(hi)IgM(neg) bone marrow pre-B cell compartment was augmented in CD69 (-/-) mice. In addition, the absence of CD69 led to a slight increase in immunoglobulin (Ig) G2a and IgM responses to immunization with T-dependent and T-independent antigens. Nevertheless, CD69-deficient lymphocytes had a normal proliferative response to different T-cell and B-cell stimuli. Together, these observations indicate that CD69 plays a role in B-cell development and suggest that the putative stimulatory activity of this molecule on bone marrow-derived cells may be replaced in vivo by other signal transducing receptors.

Animals↗
PubMed1999

Pyrrolidine dithiocarbamate protects mice from lethal shock induced by LPS or TNF-alpha.

Although important advances have been made in the development of antibiotics and medical intensive care technology in recent years, systemic response to infection remains a major health problem, with growing incidence and high mortality rates. Here we demonstrate the ability of the antioxidant agent pyrrolidine dithiocarbamate (PDTC) to inhibit the in vivo activation of NF-kappaB in lung and liver tissues, as well as the systemic release of TNF-alpha in lipopolysaccharide (LPS)-treated mice. The in vivo effect of PDTC on NF-kappaB activation in liver tissues involved the inhibition of both LPS-induced I kappaB-alpha degradation and the translocation of the p50 and p65 NF-kappaB subunits to the nucleus. In addition to protecting mice against lethal LPS doses, PDTC curtailed TNF-alpha-induced lethal shock. This effect was observed even after LPS injection, and when PDTC was administered at a time when TNF-alpha was already at maximum levels in serum. PDTC-treated mice survived despite high IL-1beta and IL-6 levels, induction of VCAM-1 and ICAM-1 expression or leukocyte infiltration in tissues known to be associated with LPS-induced shock, indicating that PDTC does not act by modifying these responses. Taken together, these results indicate that PDTC interferes with the production as well as the action of TNF-alpha, and points to a possible approach toward the treatment of septic shock.

Animals↗
PubMed1998

Regulation of endothelial cell motility by complexes of tetraspan molecules CD81/TAPA-1 and CD151/PETA-3 with alpha3 beta1 integrin localized at endothelial lateral junctions.

Cell-to-cell junction structures play a key role in cell growth rate control and cell polarization. In endothelial cells (EC), these structures are also involved in regulation of vascular permeability and leukocyte extravasation. To identify novel components in EC intercellular junctions, mAbs against these cells were produced and selected using a morphological screening by immunofluorescence microscopy. Two novel mAbs, LIA1/1 and VJ1/16, specifically recognized a 25-kD protein that was selectively localized at cell-cell junctions of EC, both in the primary formation of cell monolayers and when EC reorganized in the process of wound healing. This antigen corresponded to the recently cloned platelet-endothelial tetraspan antigen CD151/PETA-3 (platelet-endothelial tetraspan antigen-3), and was consistently detected at EC cell-cell contact sites. In addition to CD151/PETA-3, two other members of the tetraspan superfamily, CD9 and CD81/ TAPA-1 (target of antiproliferative antibody-1), localized at endothelial cell-to-cell junctions. Biochemical analysis demonstrated molecular associations among tetraspan molecules themselves and those of CD151/ PETA-3 and CD9 with alpha3 beta1 integrin. Interestingly, mAbs directed to both CD151/PETA-3 and CD81/ TAPA-1 as well as mAb specific for alpha3 integrin, were able to inhibit the migration of ECs in the process of wound healing. The engagement of CD151/PETA-3 and CD81/TAPA-1 inhibited the movement of individual ECs, as determined by quantitative time-lapse video microscopy studies. Furthermore, mAbs against the CD151/PETA-3 molecule diminished the rate of EC invasion into collagen gels. In addition, these mAbs were able to increase the adhesion of EC to extracellular matrix proteins. Together these results indicate that CD81/TAPA-1 and CD151/PETA-3 tetraspan molecules are components of the endothelial lateral junctions implicated in the regulation of cell motility, either directly or by modulation of the function of the associated integrin heterodimers.

Animals↗
PubMed1998

Expression of the MAL gene in the thyroid: the MAL proteolipid, a component of glycolipid-enriched membranes, is apically distributed in thyroid follicles.

The MAL proteolipid, an integral membrane protein expressed in T lymphocytes, polarized epithelial MDCK cells, and myelin-forming cells, has been identified as a component of internal glycolipid-enriched membrane (GEM) microdomains. On the basis of its ability to induce vesicle formation by ectopic expression, MAL has been recently proposed as a component of the machinery for GEM vesiculation. Taking into account the proposed role of GEMs in polarized transport, we have investigated the expression of the MAL gene in thyroid cells. Interestingly, MAL messenger RNA species were detected in the human thyroid, whereas they were undetectable in other endocrine glands tested. Moreover, epithelial FRT cells, a polarized rat cell line of thyroid origin, also expressed MAL transcripts. Immunohistochemical analysis of thyroid follicles, with a newly developed anti-MAL monoclonal antibody, indicates that MAL distribution is restricted to the apical zone of thyroid epithelial cells. Biochemical analyses, using FRT cells, indicate exclusive residence of MAL in GEM microdomains, and these analyses allowed the identification of MAL as a major protein component of the GEM fraction in this cell line. Our results are consistent with a role for MAL as a component of GEM microdomains in thyroid epithelial cells.

Amino Acid Sequence↗
PubMed1997

Up-regulated beta1-integrin expression in autoimmune thyroid disorders.

Lymphocytic infiltration of the thyroid gland in autoimmune thyroid disorders requires, as a first step, their attachment to endothelial cells (EC) and, subsequently, interaction with thyrocytes and extracellular matrix proteins. Recent studies have focused on the pathophysiologic role of beta1-integrins as adhesion receptors for extracellular matrix proteins and as cell-to-cell adhesion receptors. In this study, we examine by flow cytometry and immunohistochemical techniques the differences in expression of beta1-integrins in thyrocytes and EC between normal thyroids and thyroid glands from patients with Graves' disease (GD) and Hashimoto's thyroiditis (HT). Remarkably, we found an up-regulated de novo expression of very late antigen (VLA)-alpha6 subunit in thyrocytes in close proximity to lymphocyte infiltrates in GD and HT thyroid glands, with no reactivity in control thyroids. Moreover, interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and IL-1beta produced a significant enhancement of VLA-alpha6 expression in vitro in thyrocytes in culture. In addition, an up-regulated expression of VLA-alpha5 and beta1 subunits was found in thyrocytes from GD and HT glands, specifically in those areas more severely inflamed. VLA-alpha2 was basally expressed in middle size and large vessels in control glands, with an increased expression in vessels of all sizes in HT and GD glands. Dendritic cells in thyroid lymphoid follicles were also positive for VLA-beta1, alpha2 and alpha6 subunits. These results indicate the existence of an up-regulatory process in the expression of beta1-integrins, particularly the alpha6 subunit, in several cell types from inflamed GD and HT thyroid glands, suggesting that these integrins could play a relevant role in localizing and perpetuating the autoimmune response in the thyroid gland in autoimmune thyroid disorders.

Adult↗
PubMed1996

Expression of functionally active alpha 4 beta 1 integrin by thymic epithelial cells.

We have investigated the expression and function of the VLA-4 heterodimer alpha 4 beta 1, a member of the beta 1 integrin subfamily, on human thymic epithelial cells (TEC) derived from cortical epithelium. The expression of the alpha 4 integrin chain was studied in four different cloned TEC lines derived from either fetal or post-natal human thymus by both flow cytometry and immunoprecipitation techniques with anti-alpha 4 MoAbs. All different cell lines assayed expressed significant levels of alpha 4, as revealed by their reactivity with MoAbs specific for distinct alpha 4 epitopes. The alpha 4 subunit expressed by TEC was associated to beta 1 but not to beta 1 chain, and displayed the characteristic 80/ 70 kD pattern of proteolytic cleavage. The VLA-4 integrin in these cells was constitutively active in terms of adhesiveness to both fibronectin and vascular cell adhesion molecule-1 (VCAM-1). In addition, this heterodimer localized to punctate regions of the cell in the area of contact with the substratum, named point contacts assessed by staining with the anti-beta 1 activation epitope 15/7 MoAb. According to the cortical origin of the TEC lines expressing VLA-4, human thymus sections stained with different anti-alpha 4 antibodies revealed the presence of cortical, and in smaller numbers medullary epithelial cells bearing alpha 4 integrin. The expression of alpha 4 in the thymus was also found in both adult and fetal rats, in which epithelial cells were also specifically stained. Altogether, our data show that VLA-4 is an additional component of the integrin repertoire of TEC, and suggest that it could have an important role in thymus epithelial cell-thymocyte interactions.

Animals↗
PubMed1996

Thyroid autoimmune disorders in patients with chronic hepatitis C before and during interferon-alpha therapy.

BACKGROUND AND AIMS: Hepatitis C virus is involved in the induction of autoimmunity and interferon can also induce hepatic and non-hepatic autoimmune reactions. This study assessed the prevalence of thyroid autoantibodies and autoimmune thyroid disorders in patients with chronic hepatitis C before and during interferon therapy. PATIENTS AND METHODS: We studied prospectively 207 patients positive for anti-HCV and viral RNA. One hundred and forty-four of them received a therapeutic trial of one year with interferon-alpha. Free thyroxine, TSH and autoantibodies to thyroglobulin and thyroid microsomes were systematically tested at entry and at weeks 12 and 24 in both untreated and treated patients. RESULTS: Sixteen of the 207 patients (7.7%) had thyroid dysfunction, including positive antithyroid antibodies in 14 (6.7%) and hypothyroidism in 10 (4.8%) prior to interferon therapy. In addition, during pretreatment evaluation one patient developed clinical hyperthyroidism after transient subclinical hypothyroidism and another had subclinical hyperthyroidism. Prevalences of positive antithyroid antibodies and hypothyroidism were significantly higher in women (14.7 and 10.5%, respectively, vs 0% in men, P < 0.01) and were directly associated with increasing age (P < 0.01). The incidence of thyroid dysfunction was also significantly higher in patients with other autoantibodies such as anti-nuclear (ANA) (P < 0.01). A trial with interferon was initiated in 144 patients and 8 of 142 (5.6%) without previous thyroid abnormalities developed thyroid dysfunction, including positive antithyroid antibodies in 7 (4.9%) and hypothyroidism in 4 (2.8%) with a prevalence again significantly higher in women (12.7 and 8.3%, respectively, vs 1% in men, P < 0.01) and also directly related to increasing age (P < 0.01). An association was found between the development of thyroid dysfunction during interferon therapy and the presence of other autoantibodies, including ANA, anti-DNA and anti-Sjögren's antibodies (P < 0.01), as well as with the induction of autoimmune hepatitis and Sjögren's syndrome (P < 0.01 and < 0.05 respectively). Thyroid abnormalities were reversed in all patients when interferon therapy was discontinued. CONCLUSIONS: No significant association was found between chronic hepatitis C and the presence of thyroid autoimmunity in female patients. On the contrary, interferon therapy induced antithyroid autoantibodies and thyroid dysfunction de novo in patients with chronic hepatitis C without pre-existing thyroid abnormalities. Thyroid dysfunction secondary to interferon was reversible after discontinuation of therapy.

Adult↗
PubMed1995

B-cell homotypic adhesion through exon-A restricted epitopes of CD45 involves LFA-1/ICAM-1, ICAM-3 interactions, and induces coclustering of CD45 and LFA-1.

Lymphocyte interactions with other leukocytes and other cell types, as well as with components of the extracellular matrix, are one of the key steps in the immune response. Three novel monoclonal antibodies (MoAbs) have been produced and selected for their ability to induce intercellular adhesion in B cells. These three MoAbs immunoprecipitated a polypeptide of 220 kD, displaying specific phosphotyrosine phosphatase activity that has been identified as CD45. These MoAbs recognize epitopes located on the alternative spliced exon-A-encoded region of CD45. These epitopes are of polypeptidic nature, but they can be masked by addition of carbohydrate during CD45 biosynthesis. Interestingly enough, CD45 epitopes recognized by these MoAbs appeared to be selectively expressed on both peripheral blood and tonsillar B lymphocytes as well as on peripheral blood natural killer (NK) cells. CD45-mediated intercellular adhesion was abrogated upon incubation with anti-leukocyte function-associated antigen 1 (anti-LFA-1), intercellular cell adhesion molecule 1 (ICAM-1), and ICAM-3 MoAbs, thus indicating that this phenomenon involved both LFA-1/ICAM-1 and LFA-1/ICAM-3 cell adhesion pathways. Moreover, CD45-mediated cell aggregation was also inhibited by preincubation with some conventional anti-CD45 MoAbs. Interestingly, the triggering of cell aggregation through CD45 induced membrane surface relocation of CD45 and LFA-1 molecules, with both of them colocalizing at cell-cell contact areas of B-cell aggregates. Studies with inhibitors of both phosphotyrosine phosphatase and tyrosine kinase activities suggest that CD45 phosphotyrosine phosphatase activity could be involved in CD45-mediated cell aggregation. Taken together, these results support the notion that CD45 is a key molecule in the regulation of LFA-1-mediated cell-cell interactions.

Antibodies, Monoclonal↗
PubMed1995

Expression and functional significance of an activation-dependent epitope of the beta 1 integrins in chronic inflammatory diseases.

The avidity of VLA integrins for their ligands can be increased by their transition to an active conformational state. This conformational change can be detected with a novel monoclonal antibody (mAb), termed 15/7, that recognizes an activation-dependent conformational epitope on the common beta 1 polypeptide of different VLA alpha beta 1 integrins. In an attempt to understand the possible role of the active conformational state of beta 1 integrins in vivo, we first investigated the expression of 15/7 epitope on T lymphocytes from patients with chronic inflammatory joint diseases. An enhanced expression of the 15/7 epitope was found in the synovial fluid (SF) T lymphocytes from these patients as compared to their peripheral blood (PB) T cells. The effect of different cytokines on the appearance of the 15/7 activation epitope in PB T lymphocytes was subsequently analyzed; interferon-gamma, interleukin-2 and, to a lower extent, tumor necrosis factor-alpha were able to induce an increased expression of the 15/7 epitope. This enhanced 15/7 expression correlated with a higher binding ability to fibronectin of cytokine-activated T cells. The presence of this activation epitope was detected in a small proportion of T lymphocytes scattered within inflammatory foci of synovial membrane from rheumatoid arthritis and thyroid glands from Hashimoto's chronic thyroiditis. We then analyzed the possible role of 15/7 epitope expression on cell adhesion in vitro. Immunofluorescence studies showed that the 15/7 epitope displayed a spot-like distribution, selectively decorating adhesive contacts of U-937 myelomonocytic cells attached to the 80 kDa proteolytic fragment of fibronectin (FN80). Furthermore, the anti-beta 1 15/7 mAb was able to induce both T lymphocyte, Jurkat and U-937 cellular binding and spreading on FN80. Altogether these results indicate that an activated conformation of beta 1 integrins is detected in vivo in lymphocyte infiltrates from chronic inflammatory conditions. The active conformations of beta 1 integrins are regulated by physiologic mediators such as cytokines, play an important role in cellular attachment and spreading, and appear to be involved in the development of inflammatory processes.

Arthritis, Rheumatoid↗
PubMed1995

Expression of vascular adhesion molecules on human endothelia in autoimmune thyroid disorders.

Cellular activation and expression of certain adhesion molecules within vascular endothelium is a critical event in leucocyte recruitment and emigration. A wide array of different adhesion receptors has been identified to mediate the interaction between endothelial cells (EC) and leucocyte subpopulations. In this study, the tissue expression of E-selectin, P-selectin, CD31, and endoglin endothelial cell adhesion molecules was studied on thyroid tissue from patients with Graves' disease (GD) and Hashimoto's thyroiditis (HT). We found an up-regulated expression of E-selectin in EC in GD and HT thyroids, specifically in those areas more severely inflamed, with no reactivity in control thyroids. P-selectin was basally expressed in postcapillary venules in control glands, with an increased expression in HT and GD glands. On the other hand, increased CD31 expression was found on perifollicular, small and large venule EC from GD and HT glands, that correlated with the severity of mononuclear infiltration. In addition, CD31 expression was observed in some intrathyroidal macrophages and T cells in close proximity to CD31+ EC. Furthermore, a markedly enhanced expression of endoglin, a transforming growth factor-beta binding protein, was mainly located on perifollicular EC and EC from small venules as well as in adjacent macrophages from GD and HT thyroid glands. This enhanced expression of E- and P-selectins, CD31 and endoglin by thyroid EC in GD and HT may reflect their ability to regulate leucocyte trafficking and activation.

Antigens, CD↗
PubMed1995

Impaired natural killer cytotoxicity in peripheral blood mononuclear cells in Graves' disease.

We studied the natural killer (NK) activity of peripheral blood mononuclear cells (PBMC) in patients with Graves' disease (GD). Peripheral blood mononuclear cells from 20 untreated hyperthyroid patients with GD showed a significantly reduced NK activity against 51 Cr-labeled K562 cells (33.9 +/- 15.9%), while in 32 euthyroid patients under antithyroid drug therapy. NK activity was similar to that of controls (46.9 +/- 17.3 and 49.9 +/- 20.2%, respectively). Furthermore, normalization of thyroid function with antithyroid drugs was associated with a significant increase and normalization of NK activity during the follow-up of nine GD patients (from 29.2 +/- 17.9 to 48.1 +/- 16.5%). This phenomenon could not be ascribed to a defective number of NK cells because the amounts of CD56+ and CD16+ cells in PBMC from both hyperthyroid and euthyroid GD patients were within normal ranges. Natural killer activity of PBMC from patients with toxic multinodular goiter was similar to that of normal controls (45 +/- 12.8 to 49.9 +/- 20%). No correlation was found between natural killer activity and serum levels of free thyroxine, TSH-inhibitory immunoglobulins, thyroidal antibodies to thryoglobulin and thyroidal microsomal antigen, dose or duration of antithyroid drug therapy. Natural killer activity from both controls and GD patients was enhanced in vitro by addition of recombinant interleukin 2 (IL-2), reaching control levels in hyperthyroid patients. These abnormalities were not associated with a defective IL-2 production by T cells, nor with a decreased IL-2R expression. We conclude that in untreated Graves' disease there is a decrease in NK cell activity in PBMC, probably dependent on the autoimmune process.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Adhesion molecules from the LFA-1/ICAM-1,3 and VLA-4/VCAM-1 pathways on T lymphocytes and vascular endothelium in Graves' and Hashimoto's thyroid glands.

Lymphocytic infiltration of the thyroid gland in autoimmune thyroid disorders requires, as a first step, their attachment to endothelial cells (EC) and subsequently, their interaction with thyrocytes and extracellular matrix proteins. A number of different ligand molecules have been identified to mediate the interaction between EC and leukocyte subpopulations. In this study, we examined by flow cytometry and immunohistochemical techniques, the expression of integrin receptors and their counter-receptors by infiltrating lymphocytes and vascular endothelium in thyroid glands from patients with Graves' disease (GD) and Hashimoto's thyroiditis (HT). A high proportion of GD intrathyroidal T lymphocytes expressed the CD69 and gp95/85 (Ea2) activation antigens as well as an increased number of LFA-alpha L, VLA-alpha 1, -alpha 4, -alpha 5, and beta 1 integrin receptors, as compared with peripheral blood T lymphocytes from the same patients. The expression of intercellular adhesion molecule (ICAM)-1 was increased in EC from GD and HT thyroids. In addition, an up-regulated de novo expression of vascular cell adhesion molecule (VCAM)-1 was found in EC in GD and HT thyroids, with no reactivity in control thyroids. Dendritic cells in thyroid lymphoid follicles were also positive for ICAM-1 and VCAM-1. In addition, most of intrathyroidal mononuclear cells expressed the ICAM-3 adhesion molecule. This enhanced expression of ICAM-1 and VCAM-1 by thyroid EC in GD and HT may reflect their ability to regulate leukocyte trafficking and activation by means of the expression of specific ligand molecules. Our data suggest that both the LFA-1/ICAM-1, ICAM-3 and VLA-4/VCAM-1 pathways could play a relevant role in localizing and perpetuating the autoimmune response in the thyroid gland in autoimmune thyroid disorders.

Antigens, CD↗
PubMed1994

Recovery of visual and endocrine function following transsphenoidal surgery of large nonfunctioning pituitary adenomas.

A series of 35 patients with non-functioning pituitary adenomas undergoing transsphenoidal surgery is presented. In most cases, the presenting symptoms were related to the mass effect of the tumor. There was no operative mortality. Before surgery, visual field defects were documented in 21 patients (60%). After surgery, excluding 3 patients with preoperative blindness, 28% regained normal vision and 67% showed variable improvement. Preoperatively, 24 patients (69%) had abnormal pituitary function, 24 (69%) had hypogonadism, 7 (20%) adrenal insufficiency, 8 (23%) hypothyroidism and 2 (6%) panhypopituitarism. After pituitary surgery, all but one patient with normal preoperative function retained it. Of the patients with hypopituitarism, 11 (46%) had variable improvement and 13 (54%) had persistent deficits. After surgery, 4 patients (57%) with adrenal insufficiency recovered normal adrenal function, 7 patients (29%) with hypogonadism recovered gonadal function and 1 patient (13%) with hypothyroidism recovered thyroid function. Prior to surgery, the presence of a normal or slightly elevated PRL and a rise in TSH after TRH and in LH after GnRH stimulation were of value in predicting possible recovery of pituitary function after surgery. These observations suggest the presence of viable pituitary tissue in these cases and point out that, in some instances, the mechanism of hypopituitarism may be compression of the portal circulation, rather than destruction of the normal pituitary gland.

Adenoma↗
PubMed1994

T lymphocyte activation in Graves' disease.

We examined the proliferative response of T lymphocytes from thirty-eight patients with Graves' disease (17 untreated thyrotoxic and 30 euthyroid on antithyroid medication) to phytohemagglutinin, anti-CD3 MoAb and phorbol esters, as well as the capacities of these lymphocytes to produce interleukin 2 and the density of interleukin 2 receptors and major histocompatibility class II antigens. We found that the response of T lymphocytes to phytohemagglutinin, anti-CD3 monoclonal antibody and phorbol esters from untreated thyrotoxic Graves' disease was significantly enhanced as compared to treated patients and normal controls. Interleukin 2 production by mitogen-triggered T lymphocytes in both treated and untreated patients with Graves' disease was comparable to that of the control population. Interleukin 2 receptor density was found to be normal, whereas that of human leukocyte antigen-DR was increased in both untreated and treated patients. Following lymphocyte stimulation, there was an increase in human leukocyte antigen-DR and interleukin 2 receptor expression in patients with untreated Graves' disease. Significant correlations were found between thyroid hormone concentration and the proliferative responses to the polyclonal mitogen phytohemagglutinin, anti-CD3 monoclonal antibody and phorbol esters in untreated Graves' patients. Furthermore, during the follow-up of 9 patients, attainment of normal thyroid function after antithyroid treatment was associated with a decrease in and normalization of T-proliferative responses. Our data reveal that active Graves' disease is associated with T cell activation and this is probably related to immunological dysregulation as well as to hyperthyroxinemia.

Antibodies, Monoclonal↗
PubMed1994

B lymphocyte binding to E- and P-selectins is mediated through the de novo expression of carbohydrates on in vitro and in vivo activated human B cells.

Cell adhesion to endothelium regulates the trafficking and recruitment of leukocytes towards lymphoid organs and sites of inflammation. This phenomenon is mediated by the expression of a number of adhesion molecules on both the endothelium and circulating cells. Activation of endothelial cells (EC) with different stimuli induces the expression of several adhesion molecules (E- and P-selectins, ICAM-1, VCAM-1), involved in their interaction with circulating cells. In this report, we have studied the binding of nonactivated and activated B cells to purified E- and P-selectins. Activated but not resting B cells were able to interact with both selectins. This binding capacity of activated B cells paralleled the induction of different carbohydrate epitopes (Lewisx, sialyl-Lewisx, CD57 and CDw65) as well as other molecules bearing these or related epitopes in myeloid cells (L-selectin, alpha L beta 2 and alpha X beta 2 integrins, and CD35) involved in the interaction of different cell types with selectins. B cells infiltrating inflamed tissues like in Hashimoto's thyroiditis, also expressed these selectin-binding carbohydrates in parallel with the expression of E-selectin by surrounding follicular dendritic cells. Moreover, the crosslinking of these selectin-binding epitopes resulted in an increased binding of B cells to different integrin ligands. Thus, in addition to the involvement of integrins, E- and P-selectins could play an important role in the interaction of B lymphocytes with the endothelium during B cell extravasation into lymphoid tissues and inflammatory foci as well as in their organization into lymphoid organs.

B-Lymphocytes↗