Ultrastructural localization of antilymphocyte globulin on viable lymphocytes by immunoperoxidase tracing.

Immunoperoxidase tracing of the interaction of antilymphocyte globulin (ALG) with intact lymphocytes of mouse thymus and spleen showed surface membrane localization by light and electron microscopy. Ultrastructural studies of sections of lymphocytes and, by `stereoscanning', of whole cells, revealed a generally regular pattern of interrupted surface binding of the labelled antibody. The findings suggest that the antigenic determinants reacting with the ALG are uniformly distributed on the plasma membrane at some 50-nm intervals.