Immunology and Hypersensitivity in the Development of Hansen's Disease

The primary immune response to M. leprae was therefore studied in rhesus monkeys with advanced SIV infection, and in SIV [-] controls. The percentages of CD4+ and CD8+ T cells were determined over 63 days postinoculation in blood and in cutaneous inoculation sites of live M. leprae and compared with flowcytometric determinations of CD4 and CD8 levels in peripheral blood and with assessment of M.leprae-specific lymphocyte proliferation in vitro. Tissue CD4+ percentages rapidly peaked during the first two weeks after M. leprae inoculation in SIV[-] monkeys, then declined to a low plateau level by day 27. Tissue CD4+ cell percentages did not reach a peak in the SIV[+] group until day 27. In both groups, however, a similar CD4 maximum of approximately 45% was observed. By day 63 the ratios and percentages in issue had declined to similar levels in both groups. During the first month after M. leprae inoculation in SIV[+] animals, CD4+ cells continued to increase at inoculation sites even though the percentage of circulating CD4+ cells declined steadily to very low levels. Compared to SIV[-] animals, SIV[+] animals also showed delayed local expression of IL-2 mRNA, and delayed onset of responsiveness to specific to M. leprae antigens in vitro. These results suggest that SIV (and 1-11V) infection disrupts early events in the response to mycobacteria which may be critical in the development of effective cellular immunity to these pathogens, but which may not be readily evident in assessment of old, established lesions.