Expression and function of I region products on immunocompetent cells. II. I region products in T-B interaction.

The anti-Lac B precursor cells from BALB/c (H-2)d mice which survive cytotoxic treatment with anti-Iak and complement will respond to Lac-KLH in culture but require more KLH helper T cells than unselected B cell populations or B cells surviving anti-Ig killing. These findings are not explainable by the classical Poisson assumption of a constant target of T-B ionteraction. We propose a T-B interaction theory with variable Ia target on the B cell surface. The theory quantitatively predicts the observed dose response relationships, and implies that Ia molecules on B cells are cell interaction structures.