Direct Anticryptococcal Activity of Rat T Cells

Publisher Summary This chapter presents a study in which the anticryptococal activity of mononuclear cells derived from various peripheral lymphoid tissues of normal rats is compared. The study also sought to determine the phenotype of effector cells and demonstrate that immunization with cryptococcal antigen enhanced the ability of rat T lymphocytes to exert cryptococcal growth inhibition capacity. Dark August (DA) rats 12–16 week old were used in this study, and the encapsulated strain of Cryptococcu neoformans used in this study was isolated from the cerebrospinal fluid of a patient with AIDS who had developed cerebral cryptococcosis. The study revealed that freshly isolated rat peripheral T lymphocytes act directly on C. neoformans to inhibit or kill it. Fractionation of lymphocytes into CD4 + and CD8 + revealed that both cell populations exerted anticryptococcal effect, although the in vitro growth inhibition mediated by the CD8 + fraction was more efficient. The rats that were given heat-killed C. neoformans developed sensitized splenic T lymphocytes with augmented ability to inhibit the in vitro growth of C. neoformans. The results of the study suggest that direct antifungal activity is a general property of T lymphocytes irrespective of the species they are derived from, but it remains to elucidate the extent of its contribution to the host defense against infectious agents.