Candida albicans: mannan and protein activation of cells from various human lymphoid organs

Challenging human lymphocytes with soluble cytoplasmic Candida albicans protein antigen (CP) and cell-wall-derived C. albicans mannan (CM) induced DNA synthesis and antibody secretion measured as plaque-forming cells (PFC) in an indirect haemolytic assay. Enriched T and B lymphocytes responded poorly to CP and CM. However, when adherent cells were added, T and B cells responded well to CM, but not to CP. Peripheral blood lymphocytes responded more strongly to CP than to CM, with peak stimulation on day 7. Bone marrow cells displayed similar DNA synthetic responses as blood lymphocytes, but peak stimulation occurred on days 4 and 5 for CP and CM, respectively. Cells from the various parenchymal organs, including adenoid, tonsil, and spleen, showed peak DNA synthesis ranging from days 3 to 5 with a tendency for CM to produce an earlier response than CP. In contrast to that observed in blood and bone marrow cells, CM induced a higher DNA synthesis in cells from parenchymal organs than CP, which gave low stimulations. PFC, like DNA synthesis, in blood and bone marrow cells responded best to CP, whereas spleen cells showed the highest response to CM. In blood and bone marrow cells, only IgG PFC were induced, but in spleen cells IgA and IgM PFC were also stimulated by CM. Fetal liver cells responded poorly to these two Candida preparations. CM but not CP stimulated DNA synthesis in umbilical cord blood lymphocytes and IgG, IgA, and IgM in spleen cells, suggesting that CM is a polyclonal activator and that CP acts as an antigen.