Ultrastructural radioautographic studies on capping and endocytosis of anti-immunoglobulin by mouse spleen lymphocytes

Summary Mouse B lymphocytes incubated at 37° with 125I‐labelled anti‐immunoglobulin antibody initially bind the labelled material in patches at the cell membrane. This is followed by a rapid redistribution and endocytosis of label. Estimations of the numbers of labelled cells and distribution of label on the cells were made rising electron microscope radioautography. Although capping and endocytosis occur very quickly, even after 2 hours a significant number of cells labelled with anti‐n still have surface patches only. Results obtained with anti‐μ are similar to those with anti‐k. The possible significance of capping and endocytosis in immune induction is discussed.