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At least 1,207 records · Page 67Linked to original sources
PubMed1992

A protein kinase C-activating phorbol ester accelerates the T cell antigen receptor-stimulated phosphatidylinositol cycle in normal human CD4+ T cells.

Ligation of the TCR on Jurkat T lymphoblastoid cells causes an 1,4,5-inositol trisphosphate-dependent rise in intracellular cytoplasmic calcium that is inhibited by PMA, a potent activator of protein kinase C. Consequently, protein kinase C is widely believed to mediate feedback inhibition of TCR-activated phospholipase C. We have now extended these studies to normal unblasted human CD4+ T lymphocytes, examining the PMA sensitivity of both the TCR complex-mediated release of total inositol-phosphates and the resynthesis of the parent phosphoinositides. In contrast to Jurkat, in which PMA inhibited release of 1,4,5-inositol trisphosphate by 60% and total inositolphosphates by 40% (50% inhibitory concentration, 5.6 nM), normal cells displayed a marked increase in anti-CD3-induced phosphatidylinositol (PI) cycling in the presence of PMA. Both total inositolphosphate release and PI resynthesis were maximally elevated (88% and 342%, respectively) by a PMA concentration that also optimally supported a subsequent proliferative response; the ED50 was at least 11.7-fold lower than that for the inhibitory effect of PMA on breakdown of total Jurkat PI. A PKC nonactivating phorbol ester had no effect. If anti-CD3 was replaced by the mitogenic lectin PHA, PI resynthesis was similarly up-regulated by PMA in these highly purified cells. The PMA up-regulatory phenomenon was not a simple consequence of cell blastogenesis, inasmuch as there was no early effect on the non-signaling-associated phosphatidylethanolamine compartment after CD3 stimulation. Thus, PKC activation appears to accelerate TCR-linked PI metabolism in normal Th cells, in contrast to the feedback inhibitor paradigm observed in Jurkat and other tumor cell systems.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

T cell receptor expression can switch on and off at a posttranslational level.

The human T acute lymphocytic leukemia cell line, SUP-T13, is a mosaic of TCR/CD3+ and TCR/CD3- cells. Individual SUP-T13 cells can spontaneously switch on and off surface TCR/CD3 expression. This switching was demonstrated by culturing and analysis of single cell clones that were TCR/CD3+ or TCR/CD3-. The rate of switching is about 10(-2)/cell per generation in either direction. This is too high to be due to a spontaneous mutation event. Furthermore, switched cells can revert at similar rates, as demonstrated by repeated cloning and reanalysis. This makes it likely that a regulatory change is responsible for switching. In support of this, all known TCR/CD3 proteins are found intracellularly in TCR/CD3- cells, and they associate with each other as in TCR/CD3+ cells. Furthermore, no structural abnormalities of the TCR/CD3 chains can be seen in TCR/CD3- cells using two-dimensional electrophoresis. However, in these cells, the chains accumulate in great excess intracellularly. This accumulation is specific to the TCR/CD3 complex, as other glycoproteins are still expressed normally on the cell surface. Thus, there is regulation of TCR expression at a posttranslational level. These TCR/CD3- cells may lead to the identification of novel protein(s) involved in glycosylating, processing, or transporting the TCR/CD3 complex. Potential loss of TCR/CD3 expression may also limit the feasibility of TCR-based therapies for T cell leukemias.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1997

Role of CD3gamma and CD3delta cytoplasmic domains in cytolytic T lymphocyte functions and TCR/CD3 down-modulation.

TCR engagement leads to down-modulation of TCR/CD3 complexes from the T cell surface. The importance of this effect in T cell physiology is unknown. Here, we characterized a CTL clone deficient in TCR/CD3 surface expression that had lost both CD3delta and CD3gamma mRNA, allowing us to address the role of these chains in the assembly, signaling, and dynamics of the TCR/CD3 complex. Expression of either CD3delta or CD3gamma alone failed to reconstitute surface expression of the TCR/CD3 complex, but reconstitution with a cytoplasmically truncated CD3delta (delta t) and a native (gamma) or cytoplasmically truncated (gamma t) human CD3gamma led to reexpression of TCR/CD3 complexes in both cases. This indicated that CD3delta and CD3gamma assume specific functions in TCR/CD3 assembly independently of their cytoplasmic domains. The delta t gamma t variant specifically killed target cells, expressed the IFN-gamma gene in response to Ag, and produced TNF-alpha in response to anti-CD3 mAb, but it was affected in CD3 ligand-induced TCR/CD3 down-modulation. Both PMA- and CD3 ligand-induced TCR/CD3 down-modulation were defective in the delta t gamma t variant, whereas the delta t gamma variants were unaffected, and previously described delta gamma t variants were affected only in PMA-induced down-modulation. Specific protein kinase C (PKC) inhibitors indicated that PMA- but not CD3 ligand-induced down-modulation was dependent on PKC activity. Thus, amino acid sequences present in either the CD3delta or CD3gamma cytoplasmic domain control ligand-induced TCR/CD3 down-modulation, and neither these sequences nor this property are required for cytolysis and IFN-gamma gene expression in response to Ag.

Animals↗
PubMed1988

CD4 molecules are associated with the antigen receptor complex on activated but not resting T cells.

To explore the relationship between CD4 and CD3/Ti on the T cell surface, we have studied a panel of Ag-specific Th cell lines and clones, as well as resting and mitogen-activated CD4+ cells. Our results show that exposure of Th cells to their specific antigenic stimuli, but not to irrelevant stimuli, induced the rapid disappearance of approximately 20 to 35% of CD3 and CD4 molecules. The modulation of these molecules was detected in less than 1 h, became maximal at 12 h, and recovered thereafter in parallel. Treatment of Th cells with anti-CD4 antibody prevented Ag-induced modulation of CD3, and treatment with anti-CD3 blocked modulation of CD4. In the absence of Ag, treatment of these cells with an antibody (WT-31) directed at a conformational determinant within CD3/Ti or with the combination of anti-CD3 antibody and goat anti-mouse Ig, also resulted in significant modulation of CD4. Similar treatment of PHA-activated CD4+ T cells with anti-CD3/Ti antibodies also induced CD4 modulation; however, the same antibodies failed to affect CD4 expression on fresh resting T cells. These results indicate that on activated, but not resting T cells, CD4 molecules can be physically associated with CD3/Ti. We postulate that this association is essential for efficient Th cell activation, and further that the ability of anti-CD4 antibodies to inhibit helper functions is due to their prevention of CD4-CD3/Ti interaction on the T cell surface.

Antigen-Antibody Reactions↗
PubMed1994

Tumor localization and therapeutic potential of an antitumor-anti-CD3 heteroconjugate antibody in human renal cell carcinoma xenograft models.

A heteroconjugate (HC) antibody, constructed with the monoclonal antibody (MoAB) Dal K29 to human renal cell carcinoma (RCC) and an anti-CD3 MoAb, could induce a very high level of lysis of human RCC cells when incubated with human peripheral blood lymphocytes (PBL) in vitro (Kerr et al., 1990, J. Immunol., 144, 4060-4067). We now report that this HC antibody selectively localizes in RCC xenografts in nude mice and could inhibit RCC in an ascites tumor xenograft model when administered intraperitoneally together with PBL.

Animals↗
PubMed1991

Cytological characteristics of human glioma-infiltrating lymphocytes stimulated with recombinant interleukin 2 and an anti-CD3 antibody.

Tumor-infiltrating lymphocytes (TIL) were generated from 10 glioma specimens by using recombinant interleukin-2 and an anti-CD3 antibody (CD3 + TILs). We obtained more than 1 x 10(9) cells in 5 cases, more than 5 x 10(8) cells in 2 cases, and about 1 x 10(8) cells in 3 cases during three weeks of incubation from small specimens ranging in weight from 0.5 to 2.0 g. In 4 cases, TILs were expanded following stimulation with only rIL-2 (CD3-TILs). The growth rate of CD3-TILs was less than that of CD3 + TILs. Cytotoxicity of CD3 + TILs was lower than that of lymphokine-activated killer (LAK) cells in a standard 4h 51Cr release assay. Cold target inhibition was undertaken in three cases and specific cytotoxicity could be shown in only one case. CD3 + TILs mainly consisted of CD3-positive cells, ranging from 63.2 to 99.9%. The ratio of CD4-positive cells to CD8-positive cells was not constant. The expression of Leu 7 and CD16 was low. The present study did not confirm previous findings that TILs were more tumor-selective and potent than LAK cells. Furthermore, the results on in vitro antitumor activity of those cells were not necessarily consistent with the results on their clinical activity. Further careful work is necessary on the preparation of immunocytes and the subsequent adoptive immunotherapy.

Adult↗
PubMed1994

Cyclic AMP sensitive signalling by the CD28 marker requires concomitant stimulation by the T-cell antigen receptor (TCR/CD3) complex.

We have previously demonstrated that activation of cAMP-dependent protein kinase (cAK) type I (cAKI, RI alpha 2-C beta 2) mediates the inhibitory effects of cAMP on T-cell replication induced through the TCR/CD3 complex. In the present study we have investigated the effect of cAMP on T-cell DNA synthesis, tyrosine phosphorylation of a 100 kDa protein (pp100) and IL2 mRNA expression, induced through stimulation of the TCR/CD3- and/or the CD28 molecules. Our results demonstrate that tyrosine phosphorylation of pp100 stimulated by anti-CD3 is inhibited by cAMP both in the presence and absence of the phorbol ester PMA, and reflects the changes seen in IL2 mRNA expression and T-cell replication. Combined stimulation with anti-CD3 and anti-CD28, which gives a synergistic response in T-cell replication, gave pp100 phosphorylation and IL2 mRNA expression sensitive to cAMP-dependent inhibition. When PMA was added in addition to anti-CD3 and anti-CD28, the inhibitory effect of cAMP on both T-cell replication and pp100 phosphorylation was completely abolished. The fact that pp100 phosphorylation in response to TCR/CD3-, CD28- and PMA stimulation and cAMP mediated inhibition are identical to the effects of the same stimuli on T-cell proliferation, makes this protein an interesting candidate in downstream signalling from these receptors. In addition, our results are compatible with a model where cAMP, through activation of cAKI, eliminates both the PTK and PKC activating capability of the T-cell receptor at a site(s) proximal to PKC activation. Furthermore, the CD28 molecule which activates PTKs, enters the PTK cascade at a point distal to the target(s) for cAKI action. Therefore, during CD28 signalling PKC activation can be achieved either by TCR/CD3 stimulation (inhibited by cAMP), or directly by PMA (not inhibited by cAMP).

CD28 Antigens↗
PubMed1992

Enhanced tumor necrosis factor in anti-CD3 antibody stimulated diabetic NOD mice: modulation by PGE1 and dietary lipid.

Administration of OKT3 anti-CD3 monoclonal antibody (mAb) to patients for transplant rejection, is associated with a distinct and often severe clinical syndrome related to massive cytokine release. Previous reports have similarly demonstrated increased levels of serum tumor necrosis factor alpha (TNF alpha) in normal mice following administration of 1452-C11 anti-CD3 mAb. In this study, we compared serum TNF alpha levels at baseline and after anti-CD3 stimulation among three groups of mice: normal BALB/c controls, pre-diabetic non-obese diabetic (NOD) mice, and diabetic NOD mice. Baseline serum TNF alpha levels, as measured by L929 cell bioassay, were 2xhigher in diabetic NOD and 3xhigher in pre-diabetic NOD compared with BALB/c. Ninety minutes after anti-CD3 mAb stimulation, serum from BALB/c controls and pre-diabetic NOD contained 2- to 8-fold higher levels of TNF-alpha as compared to untreated control mice. In contrast, following anti-CD3 mAb, there was a dramatic 20-fold increase in serum TNF alpha in diabetic NOD mice (levels > 5000 pg/ml). Additionally, anti-CD3 mAb increased the steady-state TNF alpha mRNA transcripts. Spleens from diabetic mice given anti-CD3 mAb had higher steady-state TNF alpha mRNA than spleen from normal mice similarly treated. The enhanced release of circulating TNF alpha after anti-CD3 mAb in diabetic NOD mice was abrogated by pre-treatment of mice with prostaglandin E1 (PGE1) 30 min prior to anti-CD3 mAb stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Alprostadil↗
PubMed2002

Monophosphoryl lipid A activates both human dendritic cells and T cells.

The induction of dendritic cell (DC) maturation is critical for the induction of Ag-specific T lymphocyte responses and may be essential for the development of human vaccines relying on T cell immunity. In this study, we have investigated the effects of monophosphoryl lipid A (MPL) on human monocyte-derived DC as well as peripheral blood T cells. Calcium mobilization, mitogen-activated protein kinase activation, and the NF-kappaB transcription factor were induced after MPL stimulation of DC and required high doses of MPL (100 microg/ml). Maturation parameters such as production of IL-12 and increases in cell surface expression of HLA-DR, CD80, CD86, CD40, and CD83 were observed following DC treatment with MPL. However, lower levels of IL-12 were induced by MPL when compared with lipopolysaccharide. This is likely to be related to differences in the kinetics of extracellular signal-related kinase 1/2 and p-38 phosphorylation induced by both molecules. Although maturation induced by MPL was weaker when compared with lipopolysaccharide, it appeared to be sufficient to support optimal activation of allogeneic naive CD45RA(+) T cell and anti-tetanus toxoid CD4 T cells. MPL at low doses (5 microg/ml) had no impact on DC maturation, while its addition to DC-T cell cocultures induced full T cell activation. The observed effect was related to the fact that MPL also acts directly on T cells, likely through their Toll-like receptors, by increasing their intracellular calcium and up-regulating their CD40 ligand expression. Together, these data support a model where MPL enhances T cell responses by having an impact on DC and T cells.

Adjuvants, Immunologic↗
PubMed1992

Anti-CD3 + interleukin-2 stimulation of marrow and blood: comparison of proliferation and cytotoxicity.

The proliferation and in vitro cytolytic activity of interleukin-2 (IL-2)-activated and anti-CD3 + IL-2-stimulated marrow mononuclear cells (MMC) and peripheral blood mononuclear cells (PBMC) were studied. Samples from 8 normal donors, 15 patients with acute lymphoblastic leukemia (ALL), and 7 patients with non-Hodgkin's lymphoma (NHL) in remission were cultured in IL-2 (100 U/mL) or IL-2 (100 U/mL) plus anti-CD3 (10 ng/mL). MMC as well as PBMC samples demonstrated significant synergy between IL-2 and anti-CD3 in the promotion of proliferation as measured by 3H thymidine incorporation on day 5 (P less than .001) or fold increase in cell number on day 14. Cryopreserved marrow specimens had equally rapid proliferation as fresh MMC when cultured in the presence of anti-CD3 + IL-2. Anti-CD3 concentrations of 3, 11, 33, and 100 ng/mL augmented proliferation similarly in the presence of IL-2 (0.1 to 100 U/mL). Mean fold increases in cell number of both marrow- and blood-derived cultures after 14 days were significantly higher for anti-CD3 + IL-2-stimulated cultures compared with cultures stimulated with IL-2 only (50- to 200-fold increase in cell number; P = .01). Comparison of remission MMC and PBMC from ALL and NHL patients with normal controls showed equivalent growth rates of activated cultures at 7, 14, and 21 days. Marrow purging with immunotoxin anti-CD19 pokeweed antiviral protein plus 4HC had no significant effect on proliferation of anti-CD3 + IL-2-stimulated MMC cultures in patients with ALL. Cytolytic activity of IL-2- and IL-2 + anti-CD3-activated PBMC and MMC cultures was assessed in 51Cr release assays using K562 (natural killer ([NK]-sensitive), Daudi (Burkitt's lymphoma-, NK-resistant), and Nalm-6 (ALL-, lymphokine-activated killer [LAK]-resistant) cell lines and cryopreserved ALL blasts. Cytolytic activity on a per-cell basis (percent cytotoxicity at an effector:target ratio of 30:1) was similar in IL-2-activated PBMC- and MMC-derived cultures from ALL patients. MMC activated with anti-CD3 plus IL-2 killed Daudi significantly less well than IL-2-activated cultures on days 12 and 19 (P = .03); no significant differences were observed in lysis of LAK-resistant Nalm-6 or cryopreserved ALL blast targets. Dose response of anti-CD3 augmentation of Daudi and Nalm-6 killing was different in IL-2- and IL-2 + anti-CD3-stimulated cultures.(ABSTRACT TRUNCATED AT 400 WORDS)

Bone Marrow↗
PubMed1992

Unidirectional, heterologous desensitization of the pertussis toxin receptor by the CD3/TCR complex.

Prolonged exposure of many types of receptors to their cognate agonists can lead to a progressive lack of responsiveness. When this occurs after stimulation by the primary agonist for a given receptor it is termed homologous desensitization, and heterologous desensitization when to an agonist binding to a different type of receptor. Pertussis toxin (PTx) is a potent mitogen for human T lymphocytes. We have previously identified the human T cell PTx receptor (PTx-R) as a 43-kDa plasma membrane protein that, when stimulated, leads to the production of the intracellular second messengers, inositol-1,4,5-triphosphate, 1,2-sn-diacylglycerol, and elevated cytosolic calcium. The PTx-R appears to require the co-expression of the CD3/TCR complex because mutant cells that lack the AgR, but express the PTx-R, fail to respond to PTx. In this report, we have investigated the relationship between these two receptor systems. Activation of the PTx-R with submaximal concentrations of PTx did not affect the ability of an anti-CD3 antibody combined with rabbit anti-mIg to stimulate increases in intracellular free calcium concentration [Ca2+]i or diacylglycerol in human peripheral blood T cells. However, treatment with soluble anti-CD3 mAb, which lead to only a modest increase in [Ca2+]i, completely inhibited the effect of PTx. The cells were not refractory to further stimulation of the AgR because cross-linking with rabbit anti-mIg resulted in the standard maximal stimulation. This effect could be observed within 1 min of treatment with anti-CD3 mAb, and persisted for at least 1 h. The effect was not caused by production of either diacylglycerol (leading to activation of PK-C) or an increase in [Ca2+]i by anti-CD3 mAb because the effect could not be mimicked by either phorbol esters or a calcium ionophore. Pretreatment of either resting T lymphoblasts or PBL with anti-CD3 mAb also prevented enhanced [3H]TdR incorporation stimulated by PTx. These observations suggest a model in which T cells can regulate amplification of a non-AgR stimulatory pathway by heterologous desensitization.

Calcium↗
PubMed1994

Prevention of the humoral response induced by an anti-CD3 monoclonal antibody by deoxyspergualin in a murine model.

Multiple treatments with the potent immunosuppressant murine antihuman CD3 mAb OKT3 is sometimes precluded by the onset of a neutralizing humoral response mostly consisting of anti-idiotypic antibodies. A hamster antimurine CD3 monoclonal Ab, 145-2C11, shares many properties with OKT3, in particular the ability to induce a strong Ab response in mice. Deoxyspergulain (DSG), a metabolite of the antibiotic spergualin, has been shown to reduce Ab production triggered by pathogens in a variety of infectious models and against common antigens. In this study, we examined the ability of DSG to inhibit the humoral response induced by 145-2C11. DSG prevented the Ab production triggered by the anti-CD3 mAb in an Ag-specific manner and significantly reduced the Ab production in mice previously primed with 145-2C11. We showed that DSG had a long-term effect on B cells and a transient effect on T cells. In effect, DSG was found to induce a prolonged Ag-specific unresponsiveness of B lymphocytes, and to transiently reduce the capacity of T lymphocytes to deliver help to B cells, in part by reducing IL-4 production. DSG did not reduce the immunosuppressive properties of the anti-CD3 mAb. In fact, the combination of DSG with 145-2C11 prolonged the survival of allogeneic skin grafts when compared with the administration of 145-2C11 or DSG alone. Thus, the coadministration of DSG with OKT3 may be of clinical interest to reduce the humoral response triggered by the mAb.

Animals↗
PubMed1996

Differential interaction of the CD2 extracellular and intracellular domains with the tyrosine phosphatase CD45 and the zeta chain of the TCR/CD3/zeta complex.

T cell activation via CD2 requires interaction of CD2 with several signaling molecules. To investigate the structural requirements for an association of CD2 with the tyrosine phosphatase CD45 and the zeta chain of the T cell receptor (TCR)/CD3/zeta complex, we have expressed in mouse EL4 T cells a series of human CD2 chimeric and mutant proteins. Chimeric proteins in which the CD2 transmembrane and/or cytoplasmic domains were deleted or exchanged with analogous regions of CD4, CD28 or CD58 retained association with high levels of murine CD45 phosphatase activity, suggesting that the CD2 extracellular domain largely controls interaction with CD45. To a lesser extent, the cytoplasmic domain of CD2 was also shown to interact with CD45, as demonstrated by an increase in co-immunoprecipitated phosphatase activity observed following replacement of the CD58 cytoplasmic domain with that of CD2. In contrast, the cytoplasmic domain of CD2 was found to be responsible for the majority of CD2 interaction with the zeta chain of the TCR/CD3/zeta complex. Deletion of the CD2 cytoplasmic domain, excluding the first three amino acids, removed virtually all CD2 associated zeta chain and approximately sevenfold higher levels of zeta chain were found in association with a CD58/58/2 chimera than with control human CD58 wild type. This study suggests that the CD2 extracellular and intracellular domains are differentially involved in regulating T cell activation through interaction with the tyrosine phosphatase CD45 and the zeta chain of the TCR/CD3/zeta complex.

Animals↗
PubMed1996

A motif within the T cell receptor alpha chain constant region connecting peptide domain controls antigen responsiveness.

Mutant alphabeta TCRs were generated by replacing domains of the alpha and beta chain constant regions with homologous domains from TCR delta and gamma chains, respectively. Chimeric TCRs in which the alpha chain contains TCR delta chain sequences within the connecting peptide domain are unresponsive to alloantigens and superantigens, and have defective interactions with the CD3/zeta complex. Although these antigen-unresponsive TCRs undergo zeta chain phosphorylation upon stimulation with superantigen, they do not generate a full signal capable of producing IL-2. Mutant TCRs acquire signaling activity with a combination of superantigen and calcium ionophore, indicating a defect in calcium-mediated signaling. Finally, a conserved motif, FETDxNLN, present in the alpha chain connecting peptide domain, is disrupted in all signaling-defective TCRs. This conserved alpha chain connecting peptide motif might mediate the transfer of signals from the alphabeta heterodimer to the CD3/zeta complex.

Amino Acid Sequence↗
PubMed2001

Docking protein Gab2 is phosphorylated by ZAP-70 and negatively regulates T cell receptor signaling by recruitment of inhibitory molecules.

To maintain various T cell responses and immune equilibrium, activation signals triggered by T cell antigen receptor (TCR) must be regulated by inhibitory signals. Gab2, an adaptor protein of the insulin receptor substrate-1 family, has been shown to be involved in the downstream signaling from cytokine receptors. We investigated the functional role of Gab2 in TCR-mediated signal transduction. Gab2 was phosphorylated by ZAP-70 and co-precipitated with phosphoproteins, such as ZAP-70, LAT, and CD3zeta, upon TCR stimulation. Overexpression of Gab2 in Jurkat cells or antigen-specific T cell hybridomas resulted in the inhibition of NF-AT activation, interleukin-2 production, and tyrosine phosphorylation. The structure-function relationship of Gab2 was analyzed by mutants of Gab2. The Gab2 mutants lacking SHP-2-binding sites mostly abrogated the inhibitory activity of Gab2, but its inhibitory function was restored by fusing to active SHP-2 as a chimeric protein. A mutant with defective phosphatidylinositol 3-kinase binding capacity also impaired the inhibitory activity, and the pleckstrin homology domain-deletion mutant revealed a crucial function of the pleckstrin homology domain for localization to the plasma membrane. These results suggest that Gab2 is a substrate of ZAP-70 and functions as a switch molecule toward inhibition of TCR signal transduction by mediating the recruitment of inhibitory molecules to the TCR signaling complex.

Adaptor Proteins, Signal Transducing↗
PubMed1988

4,4'-Diisothiocyanatostilbene-2,2'-disulfonic acid inhibits CD3-T cell antigen receptor-stimulated Ca2+ influx in human T lymphocytes.

Stimulation of the CD3-T cell antigen receptor complex on T lymphocytes results in a rapid rise in intracellular calcium from both intra- and extracellular sources. The former is thought to be released from the endoplasmic reticulum in response to inositol trisphosphate, while the latter enters the cells through a membrane potential-sensitive transporter (Oettgen, H. C., Terhorst, C., Cantley, L. C., and Rosoff, P. M. (1985) Cell 40, 583-590). In this report we show that the stilbene disulfonate, DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid), inhibited the ability of monoclonal anti-CD3 complex antibodies to stimulate an influx of calcium in the human T lymphocyte cell line, Jurkat. DIDS had no effect on either antibody binding to the receptor or receptor-stimulated phosphatidylinositol turnover. The Ki was approximately 25 microM in the presence of extracellular Cl- and 10 microM when labeling was performed in the absence of Cl-, suggesting that DIDS was competing with Cl- for binding to the cell membrane. The reduced form of DIDS, dihydroDIDS, was only 50% as effective as DIDS itself, and the monoisothiocyanate stilbene, 4-acetamido-4'-isothiocyantostilbene-2,2'-disulfonic acid, was totally ineffective, even to concentrations of 0.750 mM. Removal of extracellular Cl- also inhibited the antibody-stimulated influx of calcium. These data suggest that the function of the CD3-T cell receptor-activated calcium channel/transporter may be dependent on or regulated by extracellular Cl-.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1989

The cell biology of T-dependent B cell activation.

The requirement that CD4+ helper T cells recognize antigen in association with class II Major Histocompatibility Complex (MHC) encoded molecules constrains T cells to activation through intercellular interaction. The cell biology of the interactions between CD4+ T cells and antigen-presenting cells includes multipoint intermolecular interactions that probably involve aggregation of both polymorphic and monomorphic T cell surface molecules. Such aggregations have been shown in vitro to markedly enhance and, in some cases, induce T cell activation. The production of T-derived lymphokines that have been implicated in B cell activation is dependent on the T cell receptor for antigen and its associated CD3 signalling complex. T-dependent help for B cell activation is therefore similarly MHC-restricted and involves T-B intercellular interaction. Recent reports that describe antigen-independent B cell activation through coculture with T cells activated by anti-T-cell receptor or anti-CD3 antibodies suggest that cellular interaction with T cells, independent of antigen presentation or lymphokine secretion, induces or triggers B cells to become responsive to T-derived lymphokines, and that this may be an integral component of the physiological, antigen- and MHC-restricted T-dependent B cell activation that leads to antibody production.

Animals↗