We have investigated the course of infection of Balb/c mice with Candida albicans. After intravenous infection of mice, the yeasts were evenly distributed in the liver sections. There was a 90% reduction in the yeasts found within 7 days after infection. This reduction was accompanied by an increase in the number of phagocytic cells (Mac-1(+), Gr-1(+)) in cellular infiltrates around the yeast cells. Furthermore, both CD4(+) and CD8(+) T lymphocytes were found in these pseudogranulomata, with the CD8(+) cells in the periphery. Peak amounts of the cell types investigated were found at days 5 and 6 post infection, with an increased expression of receptors for interleukin 2 (IL-2R) on the surface of CD8(+) cells. At day 14 of infection, the same levels as those in control mice were reached. At this time, the yeasts were virtually eliminated from the liver. By using simultaneous detection of cell surface markers and yeast cells in immunohistology, these data demonstrate the close association of fungal cells, phagocytes, T-H and T-c cells in pseudogranulomata during elimination of Candida albicans from the livers of mice.

We have investigated the course of infection of Balb/c mice with Candida albicans. After intravenous infection of mice, the yeasts were evenly distributed in the liver sections. There was a 90% reduction in the yeasts found within 7 days after infection. This reduction was accompanied by an increase in the number of phagocytic cells (Mac-1+, Gr-1+) in cellular infiltrates around the yeast cells. Furthermore, both CD4+ and CD8+ T lymphocytes were found in these pseudogranulomata, with the CD8+ cells in the periphery. Peak amounts of the cell types investigated were found at days 5 and 6 post infection, with an increased expression of receptors for interleukin 2 (IL-2R) on the surface of CD8+ cells. At day 14 of infection, the same levels as those in control mice were reached. At this time, the yeasts were virtually eliminated from the liver. By using simultaneous detection of cell surface markers and yeast cells in immunohistology, these data demonstrate the close association of fungal cells, phagocytes, TH and TC cells in pseudogranulomata during elimination of Candida albicans from the livers of mice.

Listeria monocytogenes belongs to the group of intracellular bacteria, which means that they reside and multiply within host cells. The protective immunity against such an infection is mediated by cellular immune mechanisms. Whereas the CD8+ T cell population plays a major role therein, the CD4+ T cells are held to be of minor importance in this defence system. Consequently, one can understand that immune suppression with FK 506 which acts primarily on this latter T cell subset, does not interfere with protective immunity of mice infected with L. monocytogenes. We have demonstrated that the drug blocks neither curing of primary infection, nor formation of granulomas, nor induction of cell populations capable of mediating adoptive transfer of immunity, nor expression of pre-existing immunity.