Rm. Syme et al., BOTH CD4(-LYMPHOCYTES ARE ACTIVATED AND PROLIFERATE IN RESPONSE TO CRYPTOCOCCUS-NEOFORMANS() AND CD8(+) HUMAN), Immunology, 92(2), 1997, pp. 194-200
The current studies were performed to determine the contribution of T-
cell subsets to lymphocyte proliferation in response to Cryptococcus n
eoformans, the most common invasive mycosis in acquired immune deficie
ncy syndrome. We demonstrate for the first time that both human CD4 an
d CD8 cells are activated in response to C. neoformans. Both CD4 and C
D8 cells express interleukin-2 receptor alpha (IL-2R alpha) and transf
errin receptor and proliferate in response to C. neoformans, however p
roliferation of CD8 cells was dependent upon CD4 cells. The requiremen
t for CD4 cells was complex, since CD8-enriched cells failed to expres
s mRNA for IL-2 suggesting that CD4-dependent IL-2 production was requ
ired for CD8-cell proliferation. However, IL-2 was not sufficient to r
estore CD8-cell proliferation. These studies provide experimental evid
ence in humans to support the clinical impression that CD4 cells are i
mportant in cryptococcosis, and suggest that the appropriate CD4-deriv
ed signals could allow CD8 cells to assist in host defence.