Antigen binding to lymphoid cells from unimmunized mice. VI. Specificity of purified multiple antigen-binding cells

In order to determine the specificity of antigen binding by double antigen-binding lymphocytes obtained from mouse bone marrow and spleen, three types of experiments were performed (1) a high excess of unlabelled antigen was tested for its ability to inhibit the binding of unrelated antigen to both single and double antigen-binding cells; (2) polyvalent anti-mouse immunoglobulin was assessed for its ability to inhibit antigen binding; and (3) the ability of one antigen to co-cap (or codistribute) with either another antigen or anti-immunoglobulin was studied to determine the spatial relationship of these components on the cell membrane. In order to study an adequate number of double ABC, these cells were enriched by using NIP-specific ABC as a starting population. The data indicate that double antigen binding occurs via independent immunoglobulin cell surface receptors which can be spatially separated from one another under appropriate capping conditions.