Failure of human blood B lymphocytes to reexpress surface IgM and IgD after treatment with anti immunoglobulin antibody

B lymphocytes in normal human blood display both IgM and IgD on their surface, most cells having both. We have removed one or both of these immunoglobulin (Ig) classes by treating the cells with class-specific anti-Ig antibody for one hour at 37°C, followed by extensive washing, thereby clearing the membrane of surface Ig by capping and endocytosis. The lymphocytes which were then cultured for 18 to 42 hours failed to show significant re-expression of the Ig class that was removed, the other Ig class being unaffected. Removal of all surface Ig by treatment with pronase allowed complete re-expression of both IgM and IgD in 18 to 42 hours. The inhibitory effect of anti-Ig was seen with both whole and Fab₂ antibody and was not reversed by subsequent treatment with pronase. Similar experiments with human spleen lymphocytes did not show this phenomenon in that both IgM and IgD were re-expressed after removal by antibody. Thus, peripheral blood B lymphocytes, but not spleen B lymphocytes, are highly sensitive to an inhibitory signal brought about by interaction with their surface Ig. This failure to re-express surface Ig after treatment with anti-Ig is identical to a defect previously described in neonatal murine spleen lymphocytes and may suggest that circulating B lymphocytes resemble immature B cells.