Mitogen-stimulated immunoglobulin production by chronic lymphocytic leukaemic lymphocytes.

The capacity of B cells from patients with chronic lymphocytic leukaemia (CLL) to produce and secrete immunoglobulin following mitogen stimulation was investigated using sensitive radioimmunoassays for mu, gamma, alpha, kappa, and lambda immunoglobulin chains. Lymphocytes from seven of the 11 patients studied secreted immunoglobulin in response to pokeweed mitogen (PWM). IgM was always the major immunoglobulin and in five of the seven responders it was the only class detected; only one type of light chain was observed in most cases. This was in contrast to normal lymphocytes which secreted all classes of immunoglobulin (IgM was invariably the lowest) containing both types of light chain. Lipopolysaccharide induced immunoglobulin secretion in only one of four CLL cases. This was again IgM with only one type of light chain. The assays are therefore most probably measuring a response by the leukaemic cells. In most CLL cases, immunoglobulin secretion by the residual normal cells, which proliferate in response to mitogen, was not observed. This inability of the normal lymphocytes to differentiate fully into immunoglobulin secreting cells and the block in switching from IgM production to other classes in the leukaemic cells may both be attributable to a defect in the regulatory system of the immune response in CLL patients.