Decreased expression of T-cell costimulatory molecule CD28 on CD4 and CD8 T cells of mexican patients with pulmonary tuberculosis.

Patients with tuberculosis frequently develop anergy, a state of T-cell hyporesponsiveness in which defective T-cell costimulation could be a factor. To know if the expression of T-cell costimulatory molecules was altered in tuberculosis, we analyzed the peripheral blood T-cell phenotype of 23 Mexican patients with pulmonary tuberculosis. There was severe CD4 (P < .001) and CD8 (P < .01) lymphopenia and upregulation of costimulatory molecule CD30 on CD4 and CD8 T cells (P < .05); this increase was higher in relapsing tuberculosis. The main finding was severe downregulation of the major costimulatory molecule CD28 on both CD8 and CD4 T cells (P < .001). Depletion of the CD4/CD28 subset, a hitherto undescribed finding, is relevant because CD4 T cells constitute the main arm of the cell-mediated antimycobacterial immune response.

Impact of opportunistic Mycobacterium tuberculosis infection on the phenotype of peripheral blood T cells of AIDS patients.

While the detrimental consequences of opportunistic tuberculosis (TB) in the course and outcome of HIV-1 infection are well studied, little information about the impact of the mycobacterial infection on the phenotype of T lymphocytes is available. In this study we analyzed by cytofluorimetry the peripheral blood T cell phenotype of 13 patients with AIDS, 23 HIV-1 negative patients with active pulmonary TB, nine HIV-1/Mycobacterium tuberculosis coinfected individuals, and 21 age- and sex-matched healthy controls. CD4+ T cells were equally depleted in AIDS and coinfection (P<0.001). The findings suggest a rescuing effect of the added mycobacterial infection. CD3 T cell loss was not observed in coinfection, whereas it was severe in AIDS (P<0.001). Similar (albeit less striking) effects were observed with other markers (CD45RA, CD45RO, and CD27) that were diminished in CD4+ T cells of AIDS patients. Apparent detrimental effects of the added mycobacterial infection were the increased expression of the proapoptotic molecule CD95 on CD4+ T cells, and decreased expression of the major costimulatory molecule CD28 on CD8+ T cells. In this work we show that M. tuberculosis infection modifies the T cell phenotype of the HIV-1 infected individual.