Heterogeneity of surface immunoglobulin on murine B lymphocytes.

Surface IgM on murine splenic lymphocytes was capped using a rhodamine-coupled anti-mu chain system. The cells were then reacted with a polyspecific, fluorescein-coupled anti-mouse immunoglobulin (Ig) under non-capping conditions. A large number (31-41% of total Ig-bearing cells) which gave red caps with anti-mu subsequently stained green peripherally with anti-Fab under the non-capping conditions. The remaining stained cells were divided between those showing only red caps (17-29% of Ig-bearing cells) and those showing only green rings (37-45% of Ig-bearing cells). These data are interpreted by assuming that most of the staining with the second reagent (fluorescein-coupled anti-mouse Ig) is due to the presence of surface associated IgD.