Chronic infections with Candida albicans have been associated with a depressed immune system. The immunosuppression associated with chronic mucocutaneous candidiasis has been defined as primarily a T-lymphocyte related phenomenon. Indeed, more recent evidence indicates that suppressor cells are activated and functioning during mucocutaneous candidiasis. Published data and preliminary results are presented which define a model for studying C. albicans-induced suppression of T-cell function. Data suggest that multiple cellular interactions are involved, and the first aim of the proposed research is to further characterize the cell types responsible. Data obtained thus far suggest the possibility that suppression is mediated by the cooperative effect of T-suppressor cells and macrophages. It is also proposed that more complete analysis of the suppresed T-cell function be carried out. The last objective of the proposed research is to determine the chemical nature of the Candida cell component(s) that is responsible for inducing the T-cell specific suppression. Analysis of various components in the cell wall and cytoplasm will be carried out, with the intention of isolating the active agent. It is believed that the proposed research will offer a significant contribution to our understanding of the nature of resistance and immunity against candidiasis, as well as a model system and new information concerning the mechanism(s) of cellular immune regulation.