Specific binding of antigen onto human T lymphocytes.

Human T lymphocytes sensitized to Candida albicans (CA) were shown to proliferate in cultures induced with mannan, a ramified polysaccharide extracted from the cell well of CA. We presently describe that, when we used strongly labeled [3H]mannan, antigen-specific T blast cells were able to bind the labeled mannan on their membrane. The observations that irrelevant blast cells did not bind [3H]mannan, and that mannan-specific blast cells did not bind tritiated pneumococcal polysaccharide SIII, indicate the specificity of mannan binding. Mannan binding was reversible and saturable. Mannan binding on T blast cells was inhibited by preincubation with monoclonal antibodies to T3 but not to other T cell-related molecules. The characteristics of this receptor suggest its identity with the T cell receptor for antigen. The direct binding of mannan could be either due to a cross-linking of the receptor by multivalent mannan or to a recognition of mannan in association with HLA-DQ molecules, as suggested by partial blocking of mannan binding using anti-HLA-DQ monoclonal antibodies.