Immune function in multiple myeloma: impaired responsiveness to keyhole limpet hemocyanin.

Twenty-three patients with multiple myeloma, four patients with treated localized plasmacytoma and 14 normal subjects were immunized with keyhole limpet hemocyanin (KLH). When compared to the normal subjects, the myeloma patients showed a prolonged induction time for IgM antibody formation, a more rapid switch from IgM to IgG production and a decline in the titre of total antibody produced. In vitro lymphocyte responses to KLH following immunization were reduced in the myeloma group and tended to decline with time in a manner similar to the serum antibody concentration. Most of the myeloma patients tested developed delayed hypersensitivity skin reactions to KLH, but these reactions were smaller than those of the control subjects. The patients with myeloma had also reduced in vitro lymphocyte responses to streptolysin-O and vaccinia. Immune function of the plasmacytoma patients was similar to that of the control subjects.Both humoral and cellular immunity in response to a newly encountered antigen, KLH, is impaired in patients with multiple myeloma.