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R Vilella

Publications and source records attributed to R Vilella.

At least 19 recordsLinked to original sources
PubMed2004

Pilot study of treatment of biochemotherapy-refractory stage IV melanoma patients with autologous dendritic cells pulsed with a heterologous melanoma cell line lysate.

Eleven AJCC stage IV melanoma patients with progressive disease after treatment with biochemotherapy were treated with autologous dendritic cells pulsed with heterologous tumor cell lysates. The vaccine used mature DCs (CD1a+++, CD40++, CD80++, CD83+, and CD86+++) generated from peripheral blood monocytes in the presence of GM-CSF and IL-4. After 7 days, DCs were matured with a defined cocktail of cytokines (IL-1+IL-6+TNF-alpha+PGE2) and simultaneously pulsed with lysates of heterologous melanoma cell lines, for 2 days. A total of 4 x 10(6) DCs was injected monthly under ultrasound control in an inguinal lymph node of normal appearance. The study was closed when all patients died as a consequence of tumor progression. No sign of toxicity was observed during the study. One patient experienced a partial response lasting 5 months, and two patients showed a mixed response which lasted 3 months. The median survival of the whole group was 7.3 months (range 3-14 months). This vaccination program had specific antitumoral activity in highly pretreated and large tumor burden stage IV melanoma patients and was well tolerated. The clinical responses and the median survival of the group of patients, together with the low toxicity of our DC vaccine, suggest that this approach could be applied to earlier AJCC stage IV melanoma patients.

Adult↗
PubMed2004

Differential expression of SAP and EAT-2-binding leukocyte cell-surface molecules CD84, CD150 (SLAM), CD229 (Ly9) and CD244 (2B4).

The CD150 (SLAM) family consists of nine leukocyte cell-surface proteins involved in lymphocyte activation that belong to the immunoglobulin (Ig) superfamily. Six members of this family--CD84, CD150 (SLAM), CD229 (Ly9), CD244 (2B4), NTB-A, and CS1--associate with adapter proteins--SLAM-associated protein (SAP) and EAT-2. SAP is a short intracellular molecule that is mutated in humans with X-linked lymphoproliferative disease. Flow cytometric analysis of the expression of CD84, CD150, CD229, and CD244 cell-surface receptors on several leukocyte and lymphocyte subsets was performed. CD84 and CD150 were present on thymocytes, mature T cells and antigen-presenting cells. The expression of CD84 and CD150 was high on memory T cells. CD150 expression was strongly up-regulated after cell activation. In contrast to CD84, CD150 was absent on resting monocytes and immature dendritic cells (DCs). CD229 presented a pattern of expression restricted to lymphocytes. CD244 was preferentially expressed on natural killer cells, CD8(+) effector cells, resting monocytes, basophils, and eosinophils. We describe a broader distribution of CD84, CD150, CD229, and CD244 than previously reported and show that they are differentially expressed on hematopoietic cells. The heterogeneous expression of these receptors indicates that these molecules may play non-redundant functions in the regulation of both innate and adaptive immune responses.

Antigens, CD↗
PubMed2001

Osteoblasts in HIV-infected patients: HIV-1 infection and cell function.

BACKGROUND: HIV-infected patients have been shown to have a severe alteration in osteoblast function that appears to be related to the infection. OBJECTIVE: To determine whether normal human osteoblasts express CD4, whether osteoblasts from patients with HIV infection are infected by HIV-1 and whether osteoblast dysfunction observed in vivo also occurs in vitro. METHODS: Osteoblast cultures from bone marrow biopsies of HIV-infected patients (n = 14) and control patients (n = 10) were used in a cross-sectional study and a case-control prospective study. Expression of CD4 was analysed using flow cytometry and reverse transcriptase polymerase chain reaction; the presence of HIV-1 particles was determined by measuring p24 antigen in the supernatants of osteoblast cultures and viral DNA or RNA in the osteoblasts using the polymerase chain reaction. Osteoblast function was assessed by measuring cell proliferation, type I collagen and osteocalcin synthesis. RESULTS: In human osteoblasts, CD4 expression could not be determined using flow cytometry, although low levels of mRNA coding for CD4 were detected. HIV infection was not observed in osteoblast cultures from HIV-infected patients nor was there any alteration in replication and synthesis of type I collagen, although osteocalcin synthesis was increased. CONCLUSIONS: It is unlikely that HIV-1 infects human osteoblasts in vivo; therefore, the hypothesis that these cells could act as local HIV-1 reservoirs should be reconsidered.

Adult↗
PubMed2001

Integrating signals from T-cell receptor and serum by T cells enhance translation of tumour necrosis factor-alpha.

Tumour necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine produced by several cell types, including T cells upon antigen stimulation. Its production is crucial for the development of an early defence against many pathogens, but its beneficial effects are dependent on the strength and duration of its expression. In this paper we present evidence indicating that serum increases translational efficiency of TNF-alpha in human peripheral blood mononuclear cells stimulated with superantigen. The increase in translation of TNF-alpha due to serum could be inhibited by the phosphatidylinositol (PI) 3-K inhibitors, wortmannin and LY294002, suggesting that PI 3-K is involved in the translational control of TNF-alpha by serum. Similarly to primary T cells, stimulation of Jurkat T cells with superantigen led to TNF-alpha secretion and this was up-regulated by serum. Transfection of Jurkat cells with a constitutively active form of PI 3-Kalpha increased the production of TNF-alpha in cells stimulated with superantigen. Additionally, we used the specific inhibitors targeting ERK kinase and p38 mitogen-activated protein kinase (MAPK), potentially downstream of PI 3-kinase, PD98059 and SB203580. Differently from with PI 3-K inhibitors, the accumulation of TNF-alpha mRNA was inhibited by PD98059 or SB203580. These results suggest that, in T cells, activation of PI 3-K is an important step in controlling TNF-alpha protein synthesis in response to growth factors.

CD4-Positive T-Lymphocytes↗
PubMed2000

Site-selective dephosphorylation of the platelet-derived growth factor beta-receptor by the receptor-like protein-tyrosine phosphatase DEP-1.

Ligand stimulation of PDGF beta-receptors leads to autophosphorylation of the regulatory tyrosine 857 and of tyrosine residues that in their phosphorylated form serve as docking sites for Src homology 2 domain-containing proteins. Regulation of the PDGF beta-receptor by protein-tyrosine phosphatases is poorly understood. We have investigated PDGF beta-receptor dephosphorylation by receptor-like protein-tyrosine phosphatase DEP-1 using a cell line with inducible DEP-1 expression and by characterizing in vitro dephosphorylation of the PDGF beta-receptor and of receptor-derived phosphopeptides by DEP-1. After DEP-1 induction PDGF beta-receptor.DEP-1 complexes and reduced receptor tyrosine phosphorylation were observed. Phosphopeptide analysis of the PDGF beta-receptors from DEP-1-expressing cells and of the receptors dephosphorylated in vitro by DEP-1 demonstrated that dephosphorylation of autophosphorylation sites of the receptor differed and revealed that the regulatory Tyr(P)(857) was not a preferred site for DEP-1 dephosphorylation. When dephosphorylation of synthetic receptor-derived peptides was analyzed, the selectivity was reproduced, indicating that amino acid sequence surrounding the phosphorylation sites is the major determinant of selectivity. This notion is supported by the observation that the poorly dephosphorylated Tyr(P)(562) and Tyr(P)(857), in contrast to other analyzed phosphorylation sites, are surrounded by basic amino acid residues at positions -4 and +3 relative to the tyrosine residue. Our study demonstrates that DEP-1 dephosphorylation of the PDGF beta-receptor is site-selective and may lead to modulation, rather than general attenuation, of signaling.

Amino Acid Sequence↗
PubMed2000

Genomic characterization of CD84 reveals the existence of five isoforms differing in their cytoplasmic domains.

CD84, a new member of the immunoglobulin superfamily, shows high homology with several molecules belonging to the CD2 family of differentiation antigens. By screening a peripheral blood leukocyte cDNA library four CD84 isoforms were obtained differing in their 3' sequence. A reverse transcription-polymerase chain reaction (RT-PCR) analysis confirmed that these isoforms were normally found on leukocytes and a new isoform was identified. To establish the nature of the five isoforms obtained (CD84a, CD84b, CD84c, CD84d and CD84e) the genomic structure of the CD84 gene was determined. Our results show that it is composed of at least eight exons, with an exon coding for the 5' UTR and the leader peptide, two exons coding for each of the two immunoglobulin-like domains, an exon encoding the transmembrane portion and four exons coding for the cytoplasmic domains. The isoforms are generated by several mechanisms: alternative use of exons, reading frame shift, use of a cryptic splice site or absence of splicing. The differential expression of several potentially phosphorylatable residues on the different isoforms could be a way to regulate its possible activity in signal transduction.

Amino Acid Sequence↗
PubMed1999

Relevance of individual CD5 extracellular domains on antibody recognition, glycosylation and co-mitogenic signalling.

CD5 is a type I glycoprotein which modulates T- and B-cell receptor-mediated signals and is expressed by thymocytes, mature T cells and a subset of mature B cells. The extracellular region of CD5 is composed of three scavenger receptor cysteine-rich domains (D1, D2, D3) for which only limited functional and structural data are available. Using cell transfectants expressing ectodomain-deficient CD5 molecules or CD5 immunoglobulin fusion proteins, we analysed individual CD5 domains with respect to monoclonal antibody binding specificity, glycosylation, and co-mitogenic signalling. Our results show the presence of N-linked oligosaccharides on D1 and D2, but not on D3. D1, the most amino-terminal domain, is predicted to be the most appropriately placed domain for an interaction with a ligand. This domain is recognised by a large panel of well characterised CD5 mAbs, reflecting its higher immunogenicity. In an attempt to develop mAbs with specificity for the more conserved membrane-proximal domains, we generated a unique mAb, named 83-C4, whose binding mapped to D3. Co-stimulatory studies revealed no significant differences between anti-D1 and anti-D3 mAbs. The high interspecies conservation of D3 implies a conserved role of this domain in CD5 function and the 83-C4 mAb promises to be a valuable tool in exploring this.

Antibodies, Monoclonal↗
PubMed1999

Differential expression of alpha2-6 sialylated polylactosamine structures by human B and T cells.

We found that human peripheral B and T cells differed in the surface expression of alpha2-6 sialylated type 2 chain glycans. In contrast to B cells, T cells expressed only sialoglycans with repeated N-acetyllactosamine (Galss1-4GlcNAc) disaccharides. This finding was based on the specificity of the monoclonal antibodies HB6, HB9 (CD24), HD66 (CDw76), FB21, and CRIS4 (CDw76) with the alpha2-6 sialylated model gangliosides IV6NeuAcnLc4Cer (2-6 SPG), VI6NeuAcnLc6Cer (2-6 SnHC), VIII6NeuAcnLc8Cer (2-6 SnOC), and X6NeuAcnLc10Cer (2-6 SnDC). We found that, in addition to their common requirement of an alpha2-6 bound terminal sialic acid for binding, the antibodies displayed preferences for the length of the carbohydrate backbones. Some of them bound mainly to 2-6 SPG with one N-acetyllactosamine (LacNAc) unit (HB9, HD66); others preferentially to 2-6 SnHC and 2-6 SnOC, with two and three LacNAc units, respectively (HB6 and FB21); and one of them exclusively to very polar alpha2-6 sialylated type 2 chain antigens (CRIS4) such as to 2-6 SnOC and even more polar gangliosides with three and more LacNAc units. These specificities could be correlated with the cellular binding of the antibodies as follows: whereas all antibodies bound to human CD 19 positive peripheral B cells, their reactivity with CD3 positive T cells was either nearly lacking (HD66, HB9), intermediate (about 65%: HB6, FB21) or strongly positive (CRIS4, 95%). Thus, the binding of the antibodies to 2-6 sialylated glycans with multiple lactosamine units appeared to determine their binding to T-cells.

Amino Sugars↗
PubMed1998

CD148 is a membrane protein tyrosine phosphatase present in all hematopoietic lineages and is involved in signal transduction on lymphocytes.

Evidence is presented showing that a protein tyrosine phosphatase different from CD45 is present on the membrane of human hematopoietic cells. The molecule recognized by the monoclonal antibody 143-41, which has been classified as CD148 in the VI International Workshop on Leukocyte Differentiation Antigens, was immunopurified and sequenced. The sequence obtained from N-terminus as well as from two different CNBr-digested peptides showed a close identity with a previously described tyrosine phosphatase named HPTP-eta/DEP-1. CD148 is present on all hematopoietic lineages, being expressed with higher intensity on granulocytes than on monocytes and lymphocytes. Interestingly, whereas it is clearly present on peripheral blood lymphocytes, it is poorly expressed on different lymphoid cell lines of T and B origin. When this protein tyrosine phosphatase was cocrosslinked with CD3, an inhibition of the normally observed calcium mobilization was observed. This inhibition correlates with a decrease in phospholipase C-gamma (PLC-gamma) phosphorylation and is similar to the one observed with CD45. In addition, it is shown that the crosslinking of the CD148 alone is also able to induce an increase in [Ca2+]i. This increase is abolished in the presence of genistein and by cocrosslinking with CD45. These data, together with the induction of tyrosine phosphorylation on several substrates, including PLC-gamma, after CD148 crosslinking, suggest the involvement of a tyrosine kinase-based signaling pathway in this process. In conclusion, the data presented show that CD148 corresponds to a previously described protein tyrosine phosphatase HPTP-eta/DEP-1 and that this molecule is involved in signal transduction in lymphocytes.

Amino Acid Sequence↗
PubMed1998

Isolation of two CD50 (ICAM-3)-negative Jurkat T-cell clones and their application for analysis of CD50 function.

The leukocyte differentiation antigen CD50 (intercellular adhesion molecule-3, ICAM-3), mediates cell-cell adhesion through its ligand LFA-1 and is a transducting receptor molecule during T-cell activation. Since CD50 homologues in other species have not yet been identified, the role of this molecule can only be analyzed in human cell models. Thus, to better study CD50 function in T cells, we have obtained two CD50-negative T-cell clones, named CAMY.1 and CAMY.2. These clones were derived from the Jurkat T-cell variant PPL.1. Data from analysis of protein expression, specific mRNA content and calcium mobilization assays have confirmed the absence of functional CD50 molecules on these two clones. Thus, CAMY.1 and CAMY.2 show no CD50 expression by phenotypical and immunoprecipitation analysis. CD50-specific mRNA content is undetectable by Northern blot analysis in these clones and, only, when RT-PCR was performed could specific mRNA be detected. Additionally, CD50 cross-linking on theses clones shows no increase in intracellular calcium. Transfection of CD50 cDNA on CAMY cells restores not only CD50 surface expression, but its functional ability to induce calcium mobilization, CD69 upregulation and cell morphological changes. The CAMY.1 and CAMY.2 clones provide useful model systems to analyze CD50 function in T cells.

Animals↗
PubMed1998

[Multicenter study of intracoronary stent implantation in Rio de Janeiro].

PURPOSE: To evaluate retrospectively stent implantation (SI) in patients with coronary artery disease (CAD) performed in 7 hospitals in Rio de Janeiro. METHODS: From June/94 to December/96 2,220 procedures were performed among which we analyzed 783 SI in 660 (29.7%) patients using coronary angiography without digital subtraction. Several types of stents were used: Palmaz-Schatz (40.9%), Gianturco-Roubin (29.1%) e NIR (22.0%). Indications for SI: 1--de novo lesion (67.9%); 2) restenotic lesion (16.0%); 3) sub-optimal results after PTCA (8.2%); 4) abrupt or threatened closure after PTCA (4.9%); 5) chronic occlusion (3.0%). All stents were implanted using high pressure balloon inflation without intracoronary ultrasound guidance. Sub-acute stent thrombosis prevention, in the majority of patients (87.8%) was done with ticlopidine and aspirin. RESULTS: Early outcome: a) the success rate of SI in 770 lesions was 98.0% in 646 (97.9%) patients; b) the clinical success rate in 634 patients was 96.0%; c) the major complications were acute myocardial infarction (1.1%); coronary artery bypass graft (1.4%) and death (0.8%); d) vascular complications with surgical correction and/or bleeding occurred in 3.0%. Late outcome: a) the clinical follow-up of 399 (60.4%) and the coronary angiographies of 121 patients (30.3%) showed in-stent lesion in 79 (19.8%); b) other event rates: myocardial infarction (1.5%); coronary bypass (2.3%); death: 1.0% and other PTCA or similar procedure (12.5%). CONCLUSION: This multicentric study showed that SI for CAD can be performed with safety, high early success rate, few complications and low rate of cardiac events during the late follow-up.

Adult↗
PubMed1997

Immunological factors in endometriosis-associated reproductive failure: studies in fertile and infertile women with and without endometriosis.

Immunopathophysiological mechanisms in endometriosis-associated reproductive failure were studied in appropriate populations: infertile and fertile women with and without endometriosis. The incidence of sera positive for any of the autoantibodies tested among infertile women with endometriosis (n = 25) was similar to that observed in the three control groups [unexplained infertility patients (n = 25) and fertile women with (n = 10) and without (n = 25) endometriosis]. The mean volume of peritoneal fluid was significantly elevated in women with endometriosis (both fertile and infertile) as compared with patients without endometriosis (fertile or infertile). The concentration of peritoneal fluid leukocytes and the percentage of cells positive for macrophage markers were significantly increased and the percentage of T lymphocytes significantly decreased in infertile women with endometriosis but not in patients with unexplained infertility and fertile women with endometriosis, as compared with fertile controls without endometriosis. Macrophages from infertile patients with endometriosis had higher sperm phagocytosis than did those from infertile women without endometriosis or fertile subjects with or without endometriosis. Incidences of serum and peritoneal fluid samples embryotoxic to the in-vitro development of 2-cell mouse embryos were significantly higher in infertile patients with endometriosis than in unexplained infertility patients and fertile women with or without endometriosis. It is concluded that immunological mechanisms of endometriosis-associated infertility exist but that these peritoneal immunological factors in infertile women with endometriosis are related to their subfertility rather than to the presence of ectopic endometrial implants. This is supported by the lack of immunological abnormalities observed among fertile women with endometriosis. These immunological abnormalities are lacking in patients with unexplained infertility.

Adult↗
PubMed1997

Transferrin receptor (CD71) expression in peritoneal macrophages from fertile and infertile women with and without endometriosis.

PROBLEM: Hyperactivated macrophages are implicated in the pathophysiology of endometriosis-associated infertility. This study investigates transferrin receptor expression (CD71) as a marker of hyperactivity in peritoneal macrophages of infertile patients with minimal to mild endometriosis (group 1, n = 25). METHOD OF STUDY: Expression of the activation antigen CD71 on peritoneal fluid macrophages was determined by a specific monoclonal anti-CD71 antibody using indirect immunofluorescence technique and was analyzed by flow cytometry. Three different control groups of women were used: women with unexplained infertility (group 2, n = 25), fertile women with endometriosis (group 3, n = 10), and fertile women without endometriosis (group 4, n = 25). RESULTS: The percentage of CD71 positive cells was significantly increased in infertile women with endometriosis as compared with the three control groups. There were no differences among groups 2, 3, and 4 with respect to the percentage of CD71 positive macrophages. CONCLUSIONS: Our results favor the concept that hyperactivated macrophages play a role in the pathophysiology of endometriosis-associated subfertility, a feature which is lacking in patients with unexplained infertility.

Adult↗
PubMed1996

Expression of intercellular adhesion molecule-3 (ICAM-3/CD50) in malignant lymphoproliferative disorders and solid tumors.

ICAM-3/CD50 is a recently described LFA-1 counter receptor that seems to play an important role in the initiation of immune responses. In this study we have examined the expression of ICAM-3/CD50 in a large series of human neoplasms including 101 Non-Hodgkin's lymphomas (NHL), 26 Hodgkin's disease, and 38 solid tumors to define the distribution patterns of this molecule in malignant neoplasms and their possible correlation with clinical and pathological characteristics of the patients. In NHL, ICAM-3/CD50 was expressed in almost all the tumors with a tendency to be lost in high grade lymphomas. Reed-Sternberg cells and their variants in Hodgkin's disease were always negative independently of the histological subtype of the disease. No expression was observed in tumor epithelial cells of the 38 solid tumors examined. Strong endothelial cell staining was observed in 31% of the NHL and 31% of Hodgkin's disease. ICAM-3 expression in these cases was restricted to small tumor vessels. ICAM-3 expression in endothelial cells of NHL was significantly more frequent in high grade (40%) than in low grade lymphomas (14%) (p = 0.012). In addition, tumor vessels were also positive in 29% of solid tumors independently of the histological type. No correlation was observed between ICAM-3 expression in tumor or endothelial cells and other clinical and pathological characteristics of the patients. These findings indicate that ICAM-3 expression in human tumors is restricted to hematological neoplasms with a tendency to be lost in high grade lymphomas and Hodgkin's disease. ICAM-3 is also expressed by endothelial cells from tumor-associated neovascularization in both lymphoid and solid tumors.

Animals↗
PubMed1995

CD50 (intercellular adhesion molecule-3) is expressed at higher levels on memory than on naive human T cells but induces a similar calcium mobilization on both subsets.

CD50, the intercellular adhesion molecule-3 (ICAM-3), is expressed almost exclusively on hematopoietic cells. T lymphocytes display a bimodal distribution on CD50 expression levels. It was observed that CD45RO+ cells expressed higher levels of CD50 than CD45RA+ T lymphocytes. A similar situation was observed when CD4 and CD8 subpopulations were analyzed, with CD8+ cells expressing higher levels of CD50 than CD4+ cells. When adult T lymphocytes were analyzed by three-color flow cytometry in CD8+CD45RA+ cells both CD50low and CD50high expressing cells were detected, in accordance with several memory markers on T lymphocytes, whereas only cells with a low level of CD50 were observed in CD4+CD45RA+. The different level of CD50 expression was confirmed by analyzing purified CD45RA+ and CD45RO+ T cells. Moreover, after the comparison of CD50 expression level in thymocytes, cord blood and adult T lymphocytes, a progressive increase was observed. When T cells were sorted by their intensity of CD50 expression, only CD50high cells proliferated in response to tetanus toxoid. Therefore, the phenotypic and functional analysis of adult and cord blood T lymphocytes as well as thymocytes indicates that CD50 expression increases during the maturation process of T lymphocytes: from the lowest CD50 levels present on CD1+ thymocytes, to the highest levels of CD50 on human memory T cells. In addition, we have observed that after CD50 cross-linking on human T lymphocytes, a transient increase in intracellular calcium concentration ([Ca2+]i) is produced. When CD45RA+ and CD45RO+ T cells were analyzed, in spite of the level of CD50 expression, the stimulation through CD50 induced a similar level of Ca2+ mobilization in both subpopulations, contrasting with the higher rise in [Ca2+]i induced by CD3 stimulation on CD45RA+ versus CD45RO+. These data suggest that the signal transduction pathways activated after CD50 cross-linking are, at least partially, independent of those involved after CD3 stimulation.

Adult↗
PubMed1995

Interleukin-2 receptor expression in salivary glands of patients with Sjögren's syndrome.

OBJECTIVE: To study interleukin-2 receptor (IL-2R) expression in lymphocytic and epithelial cells in salivary glands of patients with Sjögren's syndrome (SS). METHODS: Minor salivary glands of 29 patients with primary SS, 28 with secondary SS, 19 with autoimmune diseases without SS, and 17 controls were studied using immunohistochemical techniques. Sections were analyzed with 3 different antibodies reacting with CD25 molecule. RESULTS: The presence of IL-2R (CD25) was observed in minor salivary gland lymphocytic infiltrate in 26 (89.6%) primary SS, 24 (85.7%) secondary SS, and 16 (84%) autoimmune diseases without SS. CD25 antibody was expressed in epithelial cells in 12 (41%) patients with primary SS and 11 (39%) with secondary SS, but was absent in the group of autoimmune diseases without SS and the control group. CONCLUSION: The lymphocytic infiltrate of minor salivary gland expressed IL-2R in patients with primary SS, secondary SS and autoimmune diseases without SS. IL-2R expression in epithelial cells was only present in patients with primary or secondary SS.

Antibodies, Monoclonal↗
PubMed1994

CD50 (intercellular adhesion molecule 3) stimulation induces calcium mobilization and tyrosine phosphorylation through p59fyn and p56lck in Jurkat T cell line.

The leukocyte differentiation antigen, CD50, has been recently identified as the intercellular adhesion molecule 3 (ICAM-3), the third counter-receptor of leukocyte function-associated antigen 1 (LFA-1). This molecule seems to be specially involved in the adhesion events of the initial phases of the immune response. To characterize the role of CD50 in leukocyte interactions, the different molecular events induced after cross-linking of CD50 on T cell-derived Jurkat cell line have been analyzed. When cells were incubated with anti-CD50 mAbs and cross-linked with polyclonal goat anti-mouse immunoglobulins, a rise in intracellular calcium concentration ([Ca2+]i) was observed. This increase in [Ca2+]i was mainly due to the uptake of extracellular Ca2+. This Ca2+ flux involved tyrosine phosphorylations and was further increased by CD3 costimulation. These data, together with those obtained by phosphotyrosine (P-Tyr) immunoprecipitation and in vitro kinase assays, suggested the involvement of protein-tyrosine kinases (PTK) in CD50 transduction pathways. By using specific antisera, the presence of p56lck and p59fyn protein tyrosine kinases (PTK) was clearly demonstrated in the CD50 immunoprecipitates. These findings suggest that the interaction of CD50 with its natural ligand (LFA-1) may result in T lymphocyte activation events, in which CD50 could play a very active role after antigen triggering.

Animals↗