RESUMO
The role of TGF-beta TNF-alpha FasL and Bcl-2 in apoptosis of CD4 T-cells during active TB was studied. Coculture of PBMC from TB patients with neutralizing antibodies to TGF-beta or TNF-alpha decreased spontaneous (P < or = 0.05) and MTB-induced (P < or = 0.02) T-cell apoptosis by 50-90%, but effects were not additive. Interestingly, only levels of TGF-beta in supernatants correlated with rates of spontaneous and MTB-induced apoptosis. FasL surface and mRNA expression were higher in unstimulated and MTB-stimulated PBMC from patients than controls, and neutralization of FasL abrogated apoptosis of T-cells from patients only. Intracellular Bcl-2 protein was lower among unstimulated CD4 T-cells from patients than those from controls (P < or = 0.02), and MTB stimulation reduced intracellular Bcl-2 content in CD4 T-cells from patients only (P < or = 0.001). These findings may indicate that, during TB, predisposition of CD4 T-cells to apoptosis may involve both low expression of Bcl-2, and excessive expression of TGF-beta TNF-alpha and FasL.
Assuntos
Apoptose/imunologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/patologia , Tuberculose Pulmonar/imunologia , Tuberculose Pulmonar/patologia , Adolescente , Adulto , Regulação para Baixo/imunologia , Proteína Ligante Fas/biossíntese , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Mycobacterium tuberculosis/imunologia , Proteínas Proto-Oncogênicas c-bcl-2/biossíntese , Receptores Tipo II do Fator de Necrose Tumoral/antagonistas & inibidores , Receptores Tipo II do Fator de Necrose Tumoral/biossíntese , Fator de Crescimento Transformador beta/biossíntese , Tuberculose Pulmonar/metabolismo , Fator de Necrose Tumoral alfa/biossíntese , Regulação para Cima/imunologia , Receptor fas/biossíntese , Receptor fas/metabolismoRESUMO
Cellular signaling by TNF-alpha is mediated through activation of mitogen activated protein (MAP) kinases. In particular, p38 MAP kinase is activated in mononuclear phagocytes and may be important in sustaining TNF-alpha activity. Here, we compared the activation and mutual regulation of p38 MAP kinase and TNF-alpha by MTB in human alveolar macrophages (AM) and blood monocytes (MN). AM and autologous MN were prepared, and stimulated by MTB at 1:1 (bacteria/cell). MAP kinase activation was assessed by immunoprecipitation and kinase activity. TNF-alpha mRNA was assessed by real-time RT-PCR, and TNF-alpha immunoreactivity was assessed by ELISA. MTB-induced p38MAP kinase rapidly in AM as compared to MN, and inhibition of p38 MAP kinase by SB203580 reduced both TNF-alpha mRNA and protein. Activation of ERK (1/2) by MTB followed similar kinetics in both AM and MN. TNF-alpha produced by MTB sustained p38 MAP kinase activation in MN only. These data suggest that interaction of resident pulmonary macrophages and the more immature MN with MTB differ with regard to both p38 MAP kinase activation and TNF-alpha expression.
