Diminished synthesis of immunoglobulin by peripheral lymphocytes of patients with idiopathic membranous glomerulonephropathy.

Some studies of animal models of serum-sickness nephritis have shown that the lesions of membranous nephropathy develop in animals exhibiting a poor antibody response to the administered antigen (if given in constant amounts). It is postulated that patients with idiopathic membranous nephropathy may share a similar characteristic, namely, a diminished capacity to produce sufficient amounts of antibody. To test this hypothesis, we examined the ability of lymphocytes isolated from 11 patients with this disorder to produce immunoglobulin (Ig)G and IgM on stimulation with a polyclonal B-cell activator, pokeweed mitogen. The peripheral blood lymphocytes (2 x 10(6) cells) from 24 normal individuals had geometric mean production rates of 1,779 ng for IgG, and 2,940 ng for IgM after 7 d of culture in the presence of pokeweed mitogen. By contrast, under identical conditions, lymphocytes from the 11 patients with membranous nephropathy produced significantly lower quantities of both immunoglobulins, with geometric mean concentrations of 511 ng for IgG and 439 ng for IgM. When lymphocytes from patients with membranous nephropathy were co-cultured with normal lymphocytes, the production of immunoglobulin by normal lymphocytes was depressed by 22-82%, suggesting that a population of suppressor cells was responsible for this disturbance in B-cell function. By co-culturing normal lymphocytes with patient lymphocytes depleted of either T cells or monocytes, the suppressor cell was identified as a monocyte.