51:548±556The cellular phenotypes and the expression of cytokines were studied in the lungs of mice, using immunohistochemistry, during different phases of slowly progressive primary murine tuberculosis infection. During the ®rst phase the small focal lesions in healthy mice contained predominantly interleukin-2 (IL-2)-expressing cells. A small number of tumour necrosis factor-a (TNF-a)-, monocyte chemoattractant protein-1 (MCP-1)-and IL-10-expressing cells were also present. IL-4-expressing cells were not detected. During the second phase the mice became unwell, but the bacterial counts and the size of focal lesions stabilized. IL-4-expressing cells appeared. The IL-10-, TNF-a-and MCP-1-expressing cells increased in number. On progression to phase three, the mice became seriously unwell and died rapidly. The in¯ammation spread to < 80% of the lung parenchyma. There was a marked increase in the number of IL-10-expressing cells. Expression of other cytokines was similar to that observed in the second phase. In the lesions, 3±6% of the macrophages (Mf) containing mycobacterial antigens expressed high levels of IL-10 and TNF-a. The absolute numbers of CD3-, CD4-and CD11b-expressing cells in the lesions increased with the progression of infection. The numbers of CD8 cells were reduced in the last phase of infection. The kinetics of T-lymphocyte subsets and the pattern of cytokine expression changed with the type and degree of tissue injury. The small number of Mf with a heavy load of mycobacterial antigens may be the cause of this disturbance in cytokine balance, thus leading to progression of in¯ammation.
Our previous study showed that the cell-activation responses and cytokine-secretion patterns were different in lungs and spleens of mice with slowly progressive primary Mycobacterium tuberculosis infection. The aim of the present study was to characterize the T-cell subsets in lungs and spleens of mice with a similar infection. The percentages of T-cell subsets were determined by flow cytometry and the absolute numbers were calculated. Spleens of infected mice showed a threefold expansion of CD4+ cells but no change in CD8+ cells, whereas lungs had a threefold increase of both subsets. A significant expansion of CD4-CD8-alphabeta+ [double negative (DN)alphabeta+] subsets was observed in the lungs of infected mice compared with uninfected mice. This was not the case in the spleens of infected mice. In infected mice the CD4-CD8- (DN) population preferentially expressed alphabeta-T-cell receptors (TCR) in the lungs but gammadelta-TCR in the spleens. The percentages of many T-cell subsets were significantly higher in the lungs than in the spleens of both uninfected and infected mice. However, the percentages of CD4+ and CD4-CD8+TCR- subsets in the lungs were significantly lower than in the spleens of infected mice. We also observed some previously unreported T-cell subsets: double positive-TCR- (DPTCR-), DPalphabeta+ and DPgammadelta+. So far their functions are unknown.
The aim of the present study was to assess the compartmentalized immune response, in terms of cytokine secretion and cell activation, in lungs and spleens of mice with slowly progressive primary tuberculosis. Immunocyte populations from both organs were isolated and stimulated with concanavalin A, purified protein derivatives and MPT 59. Production of interferon-␥ (IFN-␥) and interleukin-4 (IL-4) was measured using an enzyme-linked immunosorbent assay, and cell activation was measured using a tetrazolium colorimetric assay. The IFN-␥ and IL-4 levels in the supernatants of Mycobacterium tuberculosis antigen (Ag)-stimulated lung immunocytes from infected mice were higher than the levels from uninfected mice. However, only IL-4 levels were raised in the supernatants of Ag-stimulated spleen immunocytes from infected mice. Spontaneous and Ag-stimulated immunocyte activation was lower only in the lungs of infected mice compared with uninfected mice. The level of lung immunocyte activation was inversely associated with the extent of gross pulmonary pathology. In conclusion, cytokine secretion and cell activation were different between lungs and spleens in slowly progressive primary murine tuberculosis. Cytokine diversity may explain the confinement of tuberculous lesions in the lungs and the absence of lesions in the spleens of mice with slowly progressive tuberculosis.
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