RESUMO
Regulatory T cells (Tregs) migrate into peripheral sites of inflammation such as allografts undergoing rejection, where they serve to suppress the immune response. In this study, we find that â¼30-40% of human CD25(hi) FOXP3(+) CD4(+) Tregs express the peripheral CXC chemokine receptor 3 (CXCR3) and that this subset has potent immunoregulatory properties. Consistently, we observed that proliferative responses as well as IFN-γ production were significantly higher using CXCR3-depleted versus undepleted responders in the mixed lymphocyte reaction, as well as following mitogen-dependent activation of T cells. Using microfluidics, we also found that CXCR3 was functional on CXCR3(pos) Tregs, in as much as chemotaxis and directional persistence towards interferon-γ-inducible protein of 10 kDa (IP-10) was significantly greater for CXCR3(pos) than CXCR3(neg) Tregs. Following activation, CXCR3-expressing CD4(+) Tregs were maintained in vitro in cell culture in the presence of the mammalian target of rapamycin (mTOR) inhibitor rapamycin, and we detected higher numbers of circulating CXCR3(+) FOXP3(+) T cells in adult and pediatric recipients of renal transplants who were treated with mTOR-inhibitor immunosuppressive therapy. Collectively, these results demonstrate that the peripheral homing receptor CXCR3 is expressed on subset(s) of circulating human Tregs and suggest a role for CXCR3 in their recruitment into peripheral sites of inflammation.
Assuntos
Fatores de Transcrição Forkhead/imunologia , Receptores CXCR3/imunologia , Subpopulações de Linfócitos T/imunologia , Linfócitos T Reguladores/imunologia , Adulto , Movimento Celular/imunologia , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Quimiocina CXCL10/imunologia , Quimiocina CXCL10/metabolismo , Criança , Citometria de Fluxo , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Expressão Gênica , Humanos , Imunossupressores/farmacologia , Interferon gama/imunologia , Interferon gama/metabolismo , Transplante de Rim , Selectina L/genética , Selectina L/imunologia , Selectina L/metabolismo , Ativação Linfocitária/imunologia , Receptores CCR4/genética , Receptores CCR4/imunologia , Receptores CCR4/metabolismo , Receptores CXCR3/genética , Receptores CXCR3/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Sirolimo/farmacologia , Subpopulações de Linfócitos T/metabolismo , Linfócitos T Reguladores/metabolismoRESUMO
In these studies, we find that the vascular endothelial growth factor (VEGF) receptor KDR is expressed on subsets of mitogen-activated CD4(+) and CD8(+) T cells in vitro. We also found that KDR colocalizes with CD3 on mitogen-activated T cells in vitro and on infiltrates within rejecting human allografts in vivo. To evaluate whether VEGF and KDR mediate lymphocyte migration across endothelial cells (ECs), we used an in vitro live-time transmigration model and observed that both anti-VEGF and anti-KDR antibodies inhibit the transmigration of both CD4(+) and CD8(+) T cells across tumor necrosis factor α (TNFα)-activated, but not unactivated ECs. In addition, we found that interactions among CD4(+) or CD8(+) T cells and TNFα-activated ECs result in the induction of KDR on each T cell subset, and that KDR-expressing lymphocytes preferentially transmigrate across TNFα-activated ECs. Finally, using a humanized severe combined immunodeficient mouse model of lymphocyte trafficking, we found that KDR-expressing lymphocytes migrate into human skin in vivo, and that migration is reduced in mice treated with a blocking anti-VEGF antibody. These observations demonstrate that induced expression of KDR on subsets of T cells, and locally expressed VEGF, facilitate EC-dependent lymphocyte chemotaxis, and thus, the localization of T cells at sites of inflammation.
Assuntos
Movimento Celular/fisiologia , Linfócitos T/metabolismo , Fator A de Crescimento do Endotélio Vascular/metabolismo , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Animais , Anticorpos/imunologia , Anticorpos/farmacologia , Transporte Biológico/efeitos dos fármacos , Transporte Biológico/fisiologia , Western Blotting , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD8-Positivos/citologia , Linfócitos T CD8-Positivos/metabolismo , Movimento Celular/efeitos dos fármacos , Células Cultivadas , Células Endoteliais/citologia , Células Endoteliais/metabolismo , Endotélio Vascular/metabolismo , Citometria de Fluxo , Prepúcio do Pênis/metabolismo , Prepúcio do Pênis/transplante , Humanos , Recém-Nascido , Masculino , Camundongos , Camundongos SCID , Microscopia de Fluorescência , Interferência de RNA , Transplante de Pele , Linfócitos T/citologia , Transplante Heterólogo , Fator de Necrose Tumoral alfa/farmacologia , Fator A de Crescimento do Endotélio Vascular/genética , Fator A de Crescimento do Endotélio Vascular/imunologia , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/genética , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/imunologiaRESUMO
In this study, we find that CD45RO+ memory populations of CD4+ T lymphocytes express the vascular endothelial growth factor (VEGF) receptors KDR and Flt-1 at both the mRNA and protein levels. Furthermore, by Western blot analysis, we find that VEGF increases the phosphorylation and activation of ERK and Akt within CD4+CD45RO+ T cells. These VEGF-mediated signaling responses were inhibited by a KDR-specific small interfering RNA in a VEGF receptor-expressing Jurkat T cell line and by SU5416, a pharmacological KDR inhibitor, in CD4+CD45RO+ T cells. We also find that VEGF augments mitogen-induced production of IFN-gamma in a dose-dependent manner (p < 0.001) and significantly (p < 0.05) increases directed chemotaxis of this T cell subset. Collectively, our results for the first time define a novel function for VEGF and KDR in CD45RO+ memory T cell responses that are likely of great pathophysiological importance in immunity.
