Assuntos
Membrana Eritrocítica/metabolismo , Ácidos Graxos Monoinsaturados/sangue , Transtornos Psicóticos/sangue , Adolescente , Biomarcadores/sangue , Humanos , Valor Preditivo dos Testes , Transtornos Psicóticos/diagnóstico , Ensaios Clínicos Controlados Aleatórios como Assunto/psicologia , Fatores de RiscoRESUMO
Rapamycin is a fungal macrolide that inhibits the proliferation of T cells. Studies in both animals and humans have found that rapamycin significantly reduces graft rejection. However, though CD8(+) T cells are involved in graft infiltration and rejection, little is known regarding the effects of rapamycin on CD8(+) human T cell responses. In this study, we examined the mechanism of rapamycin-induced inhibition of Ag-driven activation of CD8(+) T cells. Surprisingly, a heterogeneous proliferative response in the presence of rapamycin was observed among different Ag-specific CD8(+) T cell clones; this was also observed in CD8(+) peripheral blood T cells activated with TCR cross-linking ex vivo. Inhibition of T cell proliferation by rapamycin was controlled by both the strength of signal delivered through the Ag receptor as well as the specific costimulatory signals received by the T cell. Rapamycin-resistant proliferation occurred despite inhibition of p70(s6) kinase activity. Moreover, rapamycin-resistant proliferation of the CD8(+) T cell clones was blocked by anti-IL-2 Abs, suggesting that while some of the parallel pathways triggered by IL-2R signaling are sensitive to the effects of rapamycin, others account for the Ag-driven rapamycin resistance. These data provide a new framework for examining the specific mechanism of action of rapamycin in human disease.
Assuntos
Linfócitos T CD8-Positivos/enzimologia , Linfócitos T CD8-Positivos/imunologia , Imunossupressores/farmacologia , Ativação Linfocitária/efeitos dos fármacos , Proteínas Quinases S6 Ribossômicas/metabolismo , Sirolimo/farmacologia , Anticorpos Monoclonais/metabolismo , Antígenos CD2/imunologia , Antígenos CD2/metabolismo , Antígenos CD28/imunologia , Antígenos CD28/metabolismo , Complexo CD3/imunologia , Complexo CD3/metabolismo , Antígenos CD8/imunologia , Antígenos CD8/metabolismo , Linfócitos T CD8-Positivos/efeitos dos fármacos , Linfócitos T CD8-Positivos/metabolismo , Linhagem Celular Transformada , Células Clonais , Relação Dose-Resposta a Droga , Relação Dose-Resposta Imunológica , Resistência a Medicamentos , Ativação Enzimática/efeitos dos fármacos , Ativação Enzimática/imunologia , Epitopos de Linfócito T/imunologia , Antígenos HLA-A/fisiologia , Humanos , Interleucina-2/fisiologia , Complexo Principal de Histocompatibilidade/imunologia , Modelos Imunológicos , Subpopulações de Linfócitos T/efeitos dos fármacos , Subpopulações de Linfócitos T/enzimologia , Subpopulações de Linfócitos T/imunologiaRESUMO
T cell stimulation in the absence of a second, costimulatory signal can lead to anergy or the induction of cell death. CD28 is a major T cell costimulatory receptor, the coengagement of which can prevent anergy and cell death. The CD28 receptor is a member of a complex family of polypeptides that includes at least two receptors and two ligands. Cytotoxic lymphocyte-associated molecule-4 (CTLA-4, CD152) is the second member of the CD28 receptor family. The ligands or counterreceptors for these two proteins are the B7 family members, CD80 (B7-1) and CD86 (B7-2). This article reviews the CD28/CTLA4 and CD80/CD86 families, and outlines the functional outcomes and biochemical signaling pathways recruited after CD28 ligation.
Assuntos
Antígenos CD/imunologia , Antígenos de Diferenciação/imunologia , Antígeno B7-1/imunologia , Antígenos CD28/imunologia , Imunoconjugados , Glicoproteínas de Membrana/imunologia , Linfócitos T/imunologia , Abatacepte , Animais , Antígenos CD/metabolismo , Antígenos de Diferenciação/metabolismo , Antígeno B7-1/genética , Antígeno B7-1/metabolismo , Antígeno B7-2 , Antígenos CD28/genética , Antígenos CD28/metabolismo , Antígeno CTLA-4 , Humanos , Ativação Linfocitária , Glicoproteínas de Membrana/metabolismo , Transdução de SinaisRESUMO
Ligation of either CD80 (B7-1) or CD86 (B7-2), two principal ligands for CD28, is thought to skew the immune response toward Th1 or Th2 differentiation. We have examined early signal transduction pathways recruited following T cell stimulation with either CD80 or CD86. Purified human peripheral T cells or Jurkat T cells were stimulated with Chinese hamster ovary (CHO) cells expressing either human CD80 (CHO-CD80) or human CD86 (CHO-CD86) or with anti-CD28 monoclonal antibody (mAb). In the presence of phorbol 12-myristate 13-acetate, both CHO-CD80 and CHO-CD86, like anti-CD28 mAb, were capable of stimulating cytokine production from both human peripheral T cells and Jurkat T cells. Both CHO-CD80 and CHO-CD86, in the presence of anti-CD3 mAb, costimulated NFAT-dependent transcriptional activation. Several intracellular signaling proteins, such as CBL and VAV, were phosphorylated on tyrosine in response to CD80, CD86, and anti-CD28 mAb. Surprisingly, although stimulation of Jurkat T cells with either CHO-CD80 or anti-CD28 mAb resulted in robust tyrosine phosphorylation of CD28 itself, ligation with CHO-CD86 was unable to induce detectable CD28 tyrosyl phosphorylation over a range of stimulation conditions. In addition, the association of phosphoinositide 3-kinase with CD28 and enhanced tyrosine phosphorylation of phospholipase Cgamma were seen after anti-CD28 mAb and CHO-CD80 stimulation but to a much lesser extent after CHO-CD86 stimulation. Thus, ligation of CD28 with either CD80 or CD86 leads to shared early signal transduction events such as the tyrosine phosphorylation of CBL and VAV, to NFAT-mediated transcriptional activation, and to the costimulation of interleukin-2 and granulocyte-macrophage colony-stimulating factor production. However, CD80 and CD86 also induce distinct signal transduction pathways including the tyrosine phosphorylation of CD28 and phospholipase Cgamma1 and the SH2-dependent association of phosphoinositide 3-kinase with CD28. These quantitative, if not qualitative, differences between signaling initiated by these two ligands for CD28 may contribute to functional differences (e.g. Th1 or Th2 differentiation) in T cell responses.
Assuntos
Antígenos CD/metabolismo , Antígeno B7-1/metabolismo , Antígenos CD28/metabolismo , Glicoproteínas de Membrana/metabolismo , Proteínas Nucleares , Tirosina/metabolismo , Animais , Anticorpos Monoclonais/metabolismo , Antígeno B7-2 , Células CHO , Cricetinae , Proteínas de Ligação a DNA/metabolismo , Humanos , Interleucina-2/biossíntese , Isoenzimas/metabolismo , Células Jurkat , Fatores de Transcrição NFATC , Fosfatidilinositol 3-Quinases/metabolismo , Fosfolipase C gama , Fosforilação , Transdução de Sinais , Células Th1/metabolismo , Células Th2/metabolismo , Fatores de Transcrição/metabolismo , Ativação Transcricional , Transfecção , Fosfolipases Tipo C/metabolismo , Domínios de Homologia de srcRESUMO
CD3, CD2, and CD28 are functionally distinct receptors on T lymphocytes. Engagement of any of these receptors induces the rapid tyrosine phosphorylation of a shared group of intracellular signaling proteins, including Vav, Cbl, p85 phosphoinositide 3-kinase, and the Src family kinases Lck and Fyn. Ligation of CD3 also induces the tyrosine phosphorylation of HS1, a 75-kDa hematopoietic cell-specific intracellular signaling protein of unknown function. We have examined changes in HS1 phosphorylation after differential stimulation of CD3, CD2, and CD28 to elucidate its role in T cells and to further delineate the signaling pathways recruited by these receptors. Unlike ligation of CD3, stimulation with anti-CD28 mAb or CHO cells expressing the CD28 ligands CD80 or CD86 did not lead to tyrosine phosphorylation of HS1 in Jurkat T cells. Additionally, no tyrosine phosphorylation of HS1 was induced by mitogenic pairs of anti-CD2 mAbs capable of activating the transcription factor NFAT (nuclear factor of activated T cells). Costimulation through CD28 and/or CD2 did not modulate the CD3-dependent phosphorylation of HS1. In vivo studies indicated that CD3-induced HSI phosphorylation was dependent upon both the Src family tyrosine kinase Lck and the tyrosine phosphatase CD45, did not require MEK1 kinase activity, and was regulated by protein kinase C activation. Thus, although CD3, CD28, and CD2 activate many of the same signaling molecules, they differed in their capacity to induce the tyrosine phosphorylation of HSI. Furthermore, activation-dependent tyrosine phosphorylation of HS1 was not required for NFAT transcriptional activation.