Receptors for IgA on a subpopulation of human B lymphocytes

Human B lymphocytes from peripheral blood and tonsils and leukemic B cells from patients with chronic lymphocytic leukemia (CLL) were examined for the presence of receptors for IgA. Receptors for IgA were present on 5-20% of B cells from peripheral blood of normal persons, 6-21% of B cells from tonsils removed because of chronic enlargement, and 4-10% of B cells from patients with CLL. Prior incubation of B lymphocytes in medium containing fetal calf serum was normally essential for expression of receptors for IgA. IgM and IgG receptors were also examined on B cells from tonsils and CLL. Receptors for IgM were present on a large proportion of B cells from tonsils and B cells from patients with CLL. Their detection also required incubation of B cells in medium containing fetal calf serum for 2-3 days. In one patient with CLL, IgM receptors were present on only a small proportion of B cells. No significant change in IgG receptors on B cells from tonsils or CLL was observed when freshly isolated B cells and cultured receptors on B cells progressively decreased as a consequence of shedding of free Fc receptors into the supernates.