Quantitation of immunoglobulin isotypes in chronic lymphocytic leukaemic cells compared with normal adult and neonatal lymphocytes.

Radioimmunoassays were used to measure the total cellular content of mu, gamma, alpha, delta, kappa and lambda immunoglobulin chains in peripheral blood lymphocytes from normal adults, neonates and 11 patients with chronic lymphocytic leukaemia (CLL). Normal adult lymphocytes contained all classes of immunoglobulin, but predominantly IgG, associated with both types of light chain (kappa:lambda ratio 2:1). In contrast, mu was the major heavy chain in cells from 10 of the CLL patients, and the small amount of IgG found in CLL cells was not produced by the leukaemic clone. Approximately equimolar amounts of one type of light chain were also present, indicating monoclonality. The class distribution of the immunoglobulin in the neonatal cells was intermediate between that of CLL and normal adult cells. CLL B cells had substantially less surface IgM than normal but more cytoplasmic IgM. These data demonstrate the immaturity of neonatal B cells and suggest that CLL cells are also immature--at a stage not normally found in the adult circulation.