ACTIVATION OF MACROPHAGES AND EXPANSION OF SPECIFIC T-LYMPHOCYTES IN THE LUNGS OF MICE INTRATRACHEALLY INOCULATED WITH CRYPTOCOCCUS-NEOFORMANS

A quantitative and qualitative change in inflammatory cells in the lun gs of mice after intratracheal inoculation of heat-killed Cryptococcus neoformans was examined by direct analysis of the pulmonary intrapare nchymal leucocytes. Macrophages and T and B lymphocytes increased, pea ked at day 7, and then gradually decreased to the basal level. Macroph ages were activated 7 days after the inoculation, as indicated by the enhanced expression of MHC class II, intercellular adhesion molecule-1 (ICAM-1) and Fc receptor (FcR), which have been known as their activa tion markers. T cells were also activated, as indicated by the inducti on of IL-2 receptor (IL-2R) and the enhanced expression of leucocyte f unction-associated molecule-1 (LFA-1) and ICAM-1, a pair of adhesion m olecules which have also been regarded as T cell activation markers. C D4(+) T cells preferentially accumulated in lungs, and proliferated in vitro by stimulation with heat-killed whole yeast cells, suggesting t hat at least some of the infiltrated T cells expand locally in respons e to the organisms. These results demonstrate that the activation of m acrophages and T cells reactive to C. neoformans is induced in lungs a fter intratracheal inoculation of heat-killed organisms, and suggest t hat these cells interact to eliminate organisms more efficiently from the host.