Restriction of the in vitro anti-mannan antibody response by HLA-DQ molecules

In humans, the in vitro antibody response directed towards mannan, a polysaccharide extracted from the cell wall of Candida albicans, has been previously shown to be dependent on the presence of T lymphocytes and monocytes. Evidence is now given for the existence of a genetic restriction governing this response since antibody production is achieved provided that monocytes and T lymphocytes on one side and monocytes and B lymphocytes on the other side are of the same origin. In order to delineate the restriction element governing these interactions, blocking experiments have been designed using well-defined monoclonal antibody, anti-HLA class II molecules. The results clearly indicate that the restriction element belongs to the HLA-DQ molecular series, as shown in T-cell proliferation and antibody production assays in the presence of either T cells or T-cell supernatants. Incubation of isolated cell populations (T, B lymphocytes and monocytes) with the monoclonal antibody have indicated that DQ determinants are involved in the mannan presentation by monocytes to T and B cells. The HLA-DQ mediated restriction of the in vitro immune response to mannan has been observed in all the subjects tested, suggesting that mannan epitopes are preferentially, or even only, recognized in association with an unique group of HLA-class II molecules, namely HLA-DQ.