Impaired accessory cell function of monocytes in systemic lupus erythematosus

We studied the ability of monocytes from systemic lupus erythematosus (SLE) patients to act as accessory cells in an in vitro antibody response. Depletion of monocytes from peripheral blood mononuclear cells of normal subjects caused markedly diminished immunoglobulin (Ig) production but that of SLE did not. In order to evaluate the accessory cell activity of monocytes in in vitro immunoglobulin (Ig) production, we designed an accessory cell index of monocytes in the antibody responses. The studies revealed that Ig synthesis of isologous lymphocytes, mixed with monocytes from patients with active lupus nephritis, was significantly lower than those mixed with monocytes from healthy subjects. Moreover, the addition of graded numbers of monocytes of the former to unseparated peripheral blood mononuclear cells did not alter in vitro antibody production. These results indicate that monocytes from active SLE patients have an impared accessory cell function in an in vitro antibody response with no stimulating effect on suppressor cell activity.