Role of surface IgM and IgD in the functional differentiation of human B lymphocytes: effect of papain treatment.

Short-term treatment of normal human B lymphocytes with low concentrations of papain resulted in selective and reversible removal of sIgD determinants, whereas HLA and Ia-like antigens, sIgM as well as receptors for E, C3, and FcIgG were unaffected. When studied for their capacity to generate antigen-specific direct PFC, papain-treated (delta-) B cells were highly sensitive to inactivation by even low concentrations of antigen. In addition, these cells were impaired in their ability to cooperate normally with T-helper cells or their humoral product(s).