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Biomedical subjects

C H June

Publications and source records attributed to C H June.

At least 163 records · Page 9Linked to original sources
PubMed1989

Regulation of interleukin 3 gene induction in normal human T cells.

The regulation of IL-3 gene induction in human peripheral blood T cells was studied. IL-3 gene expression was inducible by crosslinking of the T cell receptor/CD3 complex using anti-CD3 MAb G19-4. Anti-CD3-induced IL-3 gene expression was found to be limited to the CD28+ T cell subset and could be augmented by costimulating T lymphocytes with antibodies directed against CD28. IL-3 expression could also be induced by costimulation of T cells with both phorbol ester and ionomycin, which are thought to mimic the intracellular effects of T cell receptor-antigen interaction. However, unlike other lymphokines such as IL-2 or granulocyte-macrophage colony-stimulating factor, IL-3 gene expression is not induced by stimulation of cells with phorbol myristate acetate and anti-CD28. We conclude that IL-3 gene regulation is under stringent control since IL-3 gene expression occurs only in the CD28+ subset of T cells, and since IL-3 induction obligately requires increased intracellular calcium.

Adult↗
PubMed1988

Transcription of T cell antigen receptor genes is induced by protein kinase C activation.

The regulation of expression of the TCR-alpha and -beta genes was studied in the human T cell tumor line Jurkat. Treatment of the cells with PMA was shown to decrease the surface expression of the TCR-alpha/beta/CD3 complex. Subsequent to PMA-induced modulation of the TCR/CD3 complex, increases in the mRNA levels of both the TCR-alpha and -beta genes were observed reaching a maximum 12 h after stimulation. Other T cell activators were also examined for their ability to increase TCR-alpha and -beta mRNA expression. Only agents that activate protein kinase C were shown to induce expression of the TCR-alpha and -beta genes. The observed increases in TCR-alpha and -beta gene mRNA levels were not the result of a uniquely derived Jurkat subline. Similar inductions of TCR-alpha and -beta mRNA levels were observed in an independently maintained Jurkat cell line. In both cell lines, elevations of TCR gene expression was accompanied by a decline in the expression of the c-myc proto-oncogene. PMA induction of TCR-alpha and -beta mRNA was shown to occur in the presence of the protein synthesis inhibitor cycloheximide. The 1.6-kb TCR-alpha and the 1.0-kb D beta J beta C beta TCR-beta gene transcripts were fully induced in the presence of cycloheximide, whereas the 1.3-kb V beta D beta J beta C beta transcript was only partly induced in the presence of cycloheximide. Run-on transcription assays demonstrated that the increase in TCR-alpha and -beta mRNA levels could be entirely accounted for by increases in the transcription rate of both genes after PMA induction. Thus, in summary, protein kinase C stimulation leads to TCR-alpha/beta modulation in Jurkat cells and an increase in steady state TCR-alpha and -beta mRNA levels as a result of transcriptional activation of both genes.

Cell Line↗
PubMed1988

HIV-1-infected T cells show a selective signaling defect after perturbation of CD3/antigen receptor.

The binding of antigen or monoclonal antibody to the T cell receptor for antigen or the closely associated CD3 complex causes increases in the concentration of intracellular ionized calcium and subsequent cell proliferation. By measuring second messenger production in primary cultures of human immunodeficiency virus (HIV-1)--infected T cells stimulated with monoclonal antibodies specific for either CD3 or CD2, a specific impairment of membrane signaling was revealed. The HIV-1--infected T cells were unable to mobilize Ca2+ after stimulation with anti-CD3, whereas CD2-induced calcium mobilization remained intact. Furthermore, the HIV-1--infected cells proliferated poorly after CD3 stimulation, although the cells retained normal DNA synthesis in response to interleukin-2 stimulation. These results show that the signals initiated by CD2 and CD3 can be regulated independently within the same T cell; uncoupling of signal transduction after antigen-specific stimulation provides a biochemical mechanism to explain, in part, the profound immunodeficiency of patients with HIV-1 infection.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Anti-Ig-mediated proliferation of human B cells in the absence of protein kinase C.

Cross-linking of surface Ig has been shown to stimulate phosphatidylinositol hydrolysis in murine B cells, leading to increases in [Ca2+]i and activation of protein kinase C (PKC). Preliminary evidence suggests that a similar activation mechanism occurs in human B cells. We wished to examine whether anti-Ig antibody-stimulated human B cell proliferation is as dependent upon the presence of PKC as is anti-Ig-mediated murine B cell proliferation. Using highly purified, small, dense peripheral-blood B lymphocytes from healthy adult donors, we confirmed that PMA, a direct activator of PKC, is a potent mitogen for human B cells that synergizes with anti-mu antibody. Furthermore, we demonstrated that PMA treatment abolishes detectable cellular stores of immunoreactive PKC. However, after such depletion of cellular PKC, anti-mu antibody is still capable of delivering a proliferative signal to human B cells. It is unlikely that this signal occurs solely on the basis of increases in [Ca2+]i, because the calcium ionophore A23187 does not induce a proliferative response in PMA-treated B cells similar in magnitude to that seen with anti-mu. Additionally, the finding that pretreatment of B cells with PMA ablates the ability of anti-Ig antibody to mobilize intracellular and extracellular calcium also suggests that the ability of PMA to enhance anti-Ig mediated stimulation does not depend on elevations of [Ca2+]i induced by anti-Ig. Together, these observations suggest that anti-Ig signaling of human B cells may occur via other pathways in addition to the phosphatidylinositol system of calcium influx and PKC activation.

Adult↗
PubMed1988

Signal transduction through CD4 receptors: stimulatory vs. inhibitory activity is regulated by CD4 proximity to the CD3/T cell receptor.

The binding of antibody to the CD4 molecule inhibits mobilization of cytoplasmic free calcium ([Ca2+]i) in response to CD3 cross-linking on resting T cells. Similarly, when CD3 and CD4 are independently and simultaneously cross-linked, calcium mobilization is inhibited when compared to that induced by cross-linking CD3 alone. In contrast, when anti-CD4 and anti-CD3 are cross-linked together, calcium mobilization is substantially higher than from CD3 cross-linking alone. A heteroconjugate consisting of covalently bound CD3 and CD4 monoclonal antibodies (mAb) retains the ability to mobilize [Ca2+]i in CD4 cells at protein concentrations approximately two orders of magnitude lower than the free CD3 mAb, and the activity of the heteroconjugate is inhibitable by free CD4 mAb. The CD3/CD4 heteroconjugate also shows significantly greater activity in stimulation of inositol phosphate IP1, IP2 and IP3 synthesis in T cells than the CD3 mAb alone, and again the activity is inhibited by free CD4 mAb. The activity of the CD3/CD4 heteroconjugate is not simply due to oligomerization, since CD3/CD3 or CD4/CD4 homoconjugates or homoconjugate mixtures did not show increased activity. Other heteroconjugates (CD3/CD5 and CD3/CD28) were not different than the CD3/CD3 homoconjugate in their ability to increase [Ca2+]i. Purified CD4 T cells that do not respond to CD3 mAb in solution do respond to the CD3/CD4 heteroconjugate in solution by proliferating in the presence of a CD28 mAb, with a significant fraction of CD4 cells entering the second cycle within the first three days of stimulation. The CD3/CD4 heteroconjugate co-modulates the CD3 and CD4 receptors, indicating that the heteroconjugate is not simply anchoring the T cell receptor to the T cell surface like anti-CD3 on a solid surface. These results suggest that CD4 plays an active role in signal transduction when brought into close physical proximity to the CD3/T cell receptor complex during major histocompatibility complex class II-restricted antigen presentation.

Antibodies, Monoclonal↗
PubMed1988

Role of CD2 cross-linking in cytoplasmic calcium responses and T cell activation.

The relationship between the increase of intracellular free Ca2+ concentration ([Ca2+]i) in resting T cells after stimulation with monoclonal antibody (mAb) to CD2 (E rosette receptor) and the subsequent proliferation response was investigated. Although the combination of 9.6 plus 9-1 mAb to CD2 was both mitogenic and induced an increase in [Ca2+]i, cross-linking of an individual CD2 mAb on the cell surface induced an increase in [Ca2+]i without directly stimulating T cell proliferation. The [Ca2+]i response from cross-linking an individual mAb was not epitope dependent, since 21 of 21 mAb to CD2 were effective when cross-linked with a polyclonal goat anti-mouse Ig second step. The kinetics of calcium mobilization was highly dependent upon the procedure for cross-linking, since the binding of biotin-conjugated 9.6 mAb followed by avidin gave a large and rapid response, whereas cross-linking of 9.6 with an anti-kappa mAb, 187.1, caused a minimal response, and the cross-linking of 9.6 followed by a polyclonal goat anti-mouse Ig gave an intermediate response. In addition, ligation of CD2 by rosetting with sheep red blood cells alone was sufficient to cause increased [Ca2+]i. In functional studies only the procedures associated with minimal CD2 cross-linking induced proliferation of resting T cells in combination with interleukin (IL)2. The proliferation also required IL 1 or accessory cells. Cross-linking 9.6 on the cell surface also enhanced proliferation in the presence of phorbol myristate acetate or a CD28 mAb, 9.3, under conditions that were accessory cell independent. In contrast to the proliferation following stimulation with 9.6 plus 9-1, the combination of 9.6 plus 9-1 F(ab')2 fragments lost mitogenic activity. The 9.6 plus 9-1 F(ab')2 combination was similar to 9.6 cross-linking in that either could induce responsiveness to recombinant IL2 or CD28 mAb 9.3. The combination of 9.6 plus 9-1 F(ab')2 fragments was still able to increase [Ca2+]i in T cells with slow kinetics. Together these results suggest that the binding of mAb to CD2 under conditions that cause a slow rather than a rapid increase in [Ca2+]i is associated with T cell activation. Furthermore, they suggest that in studies of T cell activation, sheep erythrocyte rosette formation should not be used to isolate T cells since rosetting may effect [Ca2+]i.

Antibodies, Monoclonal↗
PubMed1988

Multiple mechanisms regulate c-myc gene expression during normal T cell activation.

Quiescent normal human T cells express low levels of steady-state c-myc mRNA as a result of low constitutive promoter utilization, a block to transcriptional elongation within the gene, and rapid degradation of c-myc mRNA in the cytoplasm. Following the activation of the T cell receptor (TCR)/CD3 complex, quiescent T cells are induced to express c-myc mRNA. Two intracellular pathways, one involving protein kinase C activation and the other mediated by increased intracellular calcium concentration, are activated by TCR/CD3 receptor stimulation. These two pathways, which can be activated by phorbol myristate acetate (PMA) and ionomycin respectively, appear to play complementary roles in the transcriptional induction of c-myc gene expression by the antigen receptor complex. Ionomycin treatment of quiescent cells leads to enhanced c-myc expression primarily as a result of increased transcriptional initiation. In contrast, PMA contributes to c-myc expression, at least in part, by decreasing the block to transcriptional elongation present within the gene. Both the PMA- and ionomycin-mediated induction of c-myc expression can be independently enhanced by stabilization of c-myc mRNA in the cytoplasm. These observations demonstrate that multiple mechanisms co-operate to regulate c-myc gene expression during normal T cell activation.

Anti-Bacterial Agents↗
PubMed1988

Examination of the inhibitory and stimulatory effects of IFN-alpha, -beta, and -gamma on human B-cell proliferation induced by various B-cell mitogens.

In order to compare the actions of interferons on the various pathways leading to human B-cell activation, we examined the effects of alpha-interferon (INF-alpha), beta-interferon (INF-beta), and gamma-interferon (INF-gamma) on B-cell responses to mitogenic stimuli which differ in their mode of B-cell stimulation. Utilizing highly purified small, dense peripheral blood B-cells or splenic lymphocytes, we demonstrate that (i) INF-alpha, -beta, and -gamma enhance human B-cell proliferation induced by cross-linking of surface Ig with either SAC or anti-mu in a dose-dependent fashion, analogous to and with a magnitude equal to or greater than that seen with human B-cell growth factor; (ii) INF-alpha and -beta but not IFN-gamma inhibit phorbol myristate acetate-mediated B-cell mitogenesis, again in a dose-dependent manner; and (iii) IFN-gamma does not effect B-cell cytoplasmic calcium ([Ca2+]i) influx, either in the resting state or following stimulation with anti-mu, making it unlikely that IFN-gamma exerts its stimulatory effects on B-cell function through changes in [Ca2+]i. Taken together, these findings suggest that all three types of interferons may have important immunoregulatory roles in B-cell activity, and that their ability to enhance or suppress B-cell activation depends on the nature of the mitogenic stimulus.

B-Lymphocytes↗
PubMed1988

Antigen-independent regulation of cytoplasmic calcium in B cells with a 12-kDa B-cell growth factor and anti-CD19.

Increases in cytoplasmic free calcium ([Ca2+]i) can be induced in resting B cells either by a low molecular weight (12-kDa) B-cell growth factor (LMW-BCGF) or by crosslinking the B-cell antigen CD19 with monoclonal antibody (mAb). LMW-BCGF causes a slow [Ca2+]i increase in peripheral blood and tonsillar B cells but has no effect on [Ca2+]i in resting T cells. B-cell [Ca2+]i responses mediated by anti-surface immunoglobulin (sIg) or anti-CD19 are potentiated by LMW-BCGF, but anti-sIg and anti-CD19 do not show additive [Ca2+]i responses. LMW-BCGF- and anti-CD19-induced [Ca2+]i signals are similar to the sIgM or sIgD-mediated signals in that they are inhibited by prior treatment with phorbol 12-myristate 13-acetate. However, LMW-BCGF- and CD19-mediated signals do not depend on the expression of sIg, since they were also observed on sIg-B-cell precursor acute lymphoblastic leukemia (ALL) cells. Both anti-CD19 and LMW-BCGF stimulated in vitro colony formation by ALL cells and showed additive effects when used together. [Ca2+]i responses to LMW-BCGF or CD19 cross-linking were also evident on certain pre-B-cell and lymphoma B-cell lines.

Antibodies, Monoclonal↗
PubMed1988

Regulation of 4F2 heavy-chain gene expression during normal human T-cell activation can be mediated by multiple distinct molecular mechanisms.

The 4F2 molecule belongs to the set of cell surface antigens which is induced following lectin- or antigen-mediated T-cell activation. The increase in 4F2 cell surface expression following lectin-mediated stimulation has been shown to be accompanied by a parallel increase in the steady-state levels of 4F2 heavy-chain (4F2HC) mRNA. The studies described in this report were designed to further elucidate the molecular mechanisms responsible for induction of 4F2HC gene expression following activation of normal resting human peripheral blood T cells. The low levels of mature 4F2HC mRNA in resting T cells were shown to be the result of a block to transcription elongation within the exon 1-intron 1 region of the 4F2HC gene rather than promoter inactivity. Phorbol myristate acetate stimulation of resting T cells resulted in a 20-fold increase in steady-state 4F2HC mRNA levels which was mediated by removal of this block to transcription elongation. The phorbol myristate acetate-induced increase in 4F2HC gene expression is distinct from previously described AP-1-mediated, phorbol ester-induced gene expression in that it requires new protein synthesis. Treatment of resting T cells with ionomycin plus PMA resulted in a 60-fold increase in 4F2HC mRNA levels. This induction was mediated by both an increase in promoter utilization and removal of the block to transcription elongation. Finally, by increasing the half-life of 4F2HC mRNA, cycloheximide treatment of resting T cells induced an approximately five fold increase in the levels of 4F2HC gene expression, although the physiologic significance of this mechanism remains unclear. These results demonstrate that the level of 4F2HC gene expression in normal peripheral blood T cells can be regulated by at least three distinct molecular pathways: (i) changes in promoter utilization, (ii) modulation of a block to transcription elongation, and (iii) alteration in mRNA stability.

Antigens, Surface↗
PubMed1987

Glucocorticoids suppress calcium mobilization and phospholipid hydrolysis in anti-Ig antibody-stimulated B cells.

Glucocorticoids have been shown to play a major role in influencing the activation of B lymphocytes. In view of our recent observation that dexamethasone exerts a marked suppressive effect on an early event in B cell activation that is stimulated by anti-Ig antibody, we investigated its activity on other stimuli that induce intracellular events similar to those produced by anti-Ig antibody. Because the intracellular events that occur after B cell stimulation with phorbol myristate acetate and the calcium ionophore A23187 appear to mimic those that occur after B cell stimulation with anti-Ig antibody, we studied whether the cellular responses elicited by these activation stimuli are affected in a similar fashion by dexamethasone. Whereas anti-Ig antibody-stimulated entry of G0 B cells to the G1 and S phase of the cell cycle was markedly suppressed by dexamethasone, phorbol myristate acetate/A23187 stimulation of these events was resistant to dexamethasone. Our finding that anti-Ig-induced cross-linking of B cell surface Ig, as measured by surface Ig capping, was not inhibited by dexamethasone suggested that corticosteroids inhibit anti-Ig-induced B cell proliferation at a step distal to membrane Ig cross-linking and proximal to phosphatidylinositol bisphosphate hydrolysis. This hypothesis is supported by experiments presented in this manuscript which demonstrate that dexamethasone inhibits anti-Ig-stimulated phosphatidylinositol bisphosphate hydrolysis. We also found that dexamethasone markedly inhibited anti-Ig antibody-stimulated increases in intracellular ionized calcium concentrations. This dexamethasone-mediated suppression is time-dependent as it is not seen when B cells are cultured with dexamethasone for less than 6 hr. Our data suggest that the immunomodulatory activity of glucocorticoids is exerted by binding to its nuclear receptor, thereby preventing the generation of second messengers required for cell activation after agonist-receptor interaction.

Animals↗
PubMed1987

Induction of calcium flux and enhancement of cytolytic activity in natural killer cells by cross-linking of the sheep erythrocyte binding protein (CD2) and the Fc-receptor (CD16).

Binding of the anti-cluster of differentiation (CD) 2 monoclonal antibody 9-1 causes an increase in the concentration of cytoplasmic-free calcium ([Ca2+]i) in cultured CD3-/CD16+ natural killer (NK) cells. This response did not occur in cultured CD3+/CD16- cytotoxic T lymphocytes (CTL). Anti-CD16 antibodies could partially block the calcium response when NK cells were stimulated with intact antibody 9-1, and antigen-binding fragment F(ab')2 of antibody 9-1 did not produce a calcium response. Thus an interaction of the 9-1 antibody with CD16 Fc receptors was required for the functional effect. The dual interaction of antibody 9-1 with both CD2 and CD16 was demonstrated by comodulation experiments. The cytolytic activity of cultured NK cells was increased by antibody 9-1 but not by F(ab')2 fragments of antibody 9-1. The enhanced lytic activity was blocked by anti-CD16 antibody, anti-CD18 antibody, and anti-CD2 antibodies that do not block the binding of antibody 9-1. This pattern was distinct from antibody-dependent cell-mediated cytotoxicity which was blocked only by the anti-CD16 antibody. Thus antibody 9-1 enhanced cytotoxicity by activating effector cells. There was no enhancement of lytic activity when F(ab')2 of antibody 9-1 were cross-linked with a polyclonal antiglobulin, even though [Ca2+]i was increased. These results show that induction of a [Ca2+]i response is not sufficient to enhance lytic activity in NK cells, and suggest that signals delivered through CD16 are necessary.

Antibodies, Monoclonal↗
PubMed1987

CD5 antibodies increase intracellular ionized calcium concentration in T cells.

The binding of a variety of monoclonal antibodies to the CD5 (T, gp67) pan T cell differentiation antigen has been shown to potentiate T cell proliferation. In this paper we show that CD5 monoclonal antibodies cause increased intracellular free calcium concentration ([Ca2+]i) in T cells. An increase in [Ca2+]i occurred within 1 min in indo-1-loaded PBMC after the addition of CD5 monoclonal antibodies and cross-linking with a second step anti-mouse kappa light chain antibody. Cross-linking of CD5 was effective when done directly on the cell surface or by the administration of preformed soluble complexes that contained CD5 antibodies. Calcium mobilization induced by suboptimal concentrations of CD3 antibodies was specifically augmented and sustained by CD5 antibodies, although the enhancement was modest in magnitude. When cell surface phenotype was correlated with calcium mobilization, it was found that the CD5 response was restricted to CD5+/CD3+ cells, and that approximately 90% of CD5+ cells had responded. CD5-induced calcium mobilization was found to differ from CD3 stimulation in that EGTA entirely ablated the CD5 response, whereas the CD3 response was resistant to EGTA, indicating that the CD5-induced increased [Ca2+]i is derived primarily or entirely from extracellular calcium. CD5-stimulated calcium mobilization also differed from CD3 in that the CD5 response was inhibited by pretreatment with phorbol myristate acetate, whereas the CD3 response was not, suggesting that depletion of protein kinase C causes an uncoupling of signal transduction between CD5 and calcium channels. Finally, experiments were done with T cells after antigenic modulation of the CD3 or CD5 molecules. Unexpectedly, both the CD5 and the CD3 responses were ablated on CD3-modulated cells, whereas only the CD5 response was ablated on CD5-modulated cells. In addition, several Cd5+/CD3- T cell leukemia lines also failed to respond to CD5 stimulation, providing further evidence which indicates that the CD5 response depends on the cell surface expression of CD3 or a CD3-associated structure. These findings suggest that one mechanism for CD5-induced augmentation of mitogen-stimulated T cell proliferation involves increased [Ca2+]i which is distinct from but interdependent with that induced by stimulation of the CD3 molecule.

Antigen-Antibody Reactions↗
PubMed1987

Crosslinking of surface antigens causes mobilization of intracellular ionized calcium in T lymphocytes.

Antibodies binding to a large subset of T-cell differentiation antigens, including CD2, CD4, CD5, CD6, CD7, CD8, Tp44, and CDw18, cause an increase in the cytoplasmic calcium concentration [( Ca2+]i) after the antigens are crosslinked on the cell surface. Similar crosslinking-induced signals were seen for a subset of mouse thymocyte differentiation antigens. The various antigens on human T cells differed in the extent of crosslinking required for generating the calcium signal, as evidenced by comparisons with monoclonal versus polyclonal second-step antibody. The [Ca2+]i increase that occurs after crosslinking represents mobilization of cytoplasmic calcium since the initial component of the signal is resistant to depletion of extracellular calcium by chelation with EGTA. The [Ca2+]i increase is completely inhibited by pretreatment of cells with pertussis toxin, indicating that a substrate for pertussis toxin regulates the signal transduction. Crosslinking of antigens other than the CD3/T-cell receptor complex did not result in T-cell proliferation. Crosslinking of CD2 and Tp44, but not other antigens, resulted in expression of functional interleukin 2 receptors. Comparisons of three different anti-CD3 antibodies showed that a second calcium signal was generated by crosslinking, even when the anti-CD3 antibodies were used at optimal concentrations.

Animals↗
PubMed1987

T-cell proliferation involving the CD28 pathway is associated with cyclosporine-resistant interleukin 2 gene expression.

CD28 is a homodimeric glycoprotein expressed on the surface of a major subset of human T cells that has recently been identified as a member of the immunoglobulin supergene family. The binding of monoclonal antibodies to the CD28 antigen on purified T cells does not result in proliferation; however, previous studies have shown that the combination of CD28 stimulation and protein kinase C activation by phorbol myristate acetate (PMA) results in T-cell proliferation that is independent of both accessory cells and activation of the T-cell receptor-CD3 complex. In the present study, effects of stimulation by anti-CD28 on cell cycle progression and on the interleukin 2 (IL-2) and IL-2 receptor system have been investigated on primary cultures of purified peripheral-blood CD28+ T cells. There was no measurable effect on cell size or on DNA synthesis after stimulation of resting (G0) cells by CD28 alone. After 3 h of activation of T cells by PMA alone, a slight (8%) increase in cell volume occurred that did not progress to DNA synthesis. In contrast, T-cell stimulation by CD28 in combination with PMA resulted in a progressive increase in cell volume in approximately 100% of cells at 12 to 14 h after stimulation. Northern blot (RNA blot) analysis revealed that CD28 stimulation alone failed to cause expression of the alpha chain of the IL-2 receptor or of IL-2 mRNA, and in accord with previous studies, stimulation by PMA alone resulted in the accumulation of IL-2 receptor transcripts but no detectable IL-2 mRNA. In contrast, T-cell stimulation by the combination of CD28 and PMA resulted in the appearance of IL-2 transcripts and enhanced expression of IL-2 receptor mRNA. Functional studies revealed that the proliferation induced by CD28 and PMA stimulation was entirely resistant to cyclosporine, in contrast to T-cell activation induced by the CD3-T-cell receptor complex. Cyclosporine was found not to affect the accumulation of IL-2 mRNA after CD28 plus PMA stimulation, although there was no detectable IL-2 mRNA after stimulation by CD3 in the presence of the drug. Furthermore, stimulation by CD28 in combination with immobilized CD3 antibodies caused a striking enhancement of IL-2 mRNA expression that was, in part, resistant to the effects of cyclosporine. These studies indicate that the CD28 molecule synergizes with protein kinase C activation to induce IL-2 gene expression and demonstrate that stimulation by the CD28 pathway can cause vigorous T-cell proliferation even in the presence of cyclosporine and that cyclosporine does not prevent transcription of 16-2 mRNA, as has been suggested previously. Moreover, these findings suggest that a potential role for the CD28 molecule in vivo may be to augment IL-2 production after stimulation of the CD3-T-cell receptor molecular complex and thereby to amplify an antigen-specific immune response. Finally, these results provide further evidence that the CD28 molecule triggers T-cell proliferation in a manner that differs biochemically from CD3-T-cell receptor-induced proliferation.

Adult↗
PubMed1987

Stimulation of T cells through the CD3/T-cell receptor complex: role of cytoplasmic calcium, protein kinase C translocation, and phosphorylation of pp60c-src in the activation pathway.

Stimulation of T cells or the Jurkat T-cell line with soluble antibodies to the CD3/T-cell receptor complex causes mobilization of cytoplasmic Ca2+, which is blocked by pertussis toxin but not by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, and translocation of protein kinase C activity from the cytoplasm to the membrane. Such stimulation also causes phosphorylation of pp60c-src at an amino-terminal serine residue. These activities are consistent with induction of phosphatidylinositol metabolism after antibody binding. Anti-CD3 stimulation with antibody in solution, however, does not cause Jurkat cells to release interleukin 2 and blocks rather than induces proliferation of T cells. Induction of interleukin 2 production by Jurkat cells and proliferation by normal T cells requires anti-CD3 stimulation with antibody on a solid support, such as Sepharose beads or a plastic dish. Thus, we examined phosphorylation of pp60c-src after stimulation of Jurkat cells with anti-CD3 in solution or on solid phase. Both of these caused serine phosphorylation of pp60c-src that was indistinguishable even after 4 h of stimulation. These results indicate that the mode of anti-CD3 stimulation (in solution or on solid phase) controls a cellular function that modifies the consequences of signal transduction through phosphatidylinositol turnover.

Antigens, Differentiation, T-Lymphocyte↗