Decreased T-cell-mediated suppression of IgM--rheumatoid factor synthesis in rheumatoid arthritis.

Circulating B-cell precursors specific for rheumatoid factor (RF) are present in normal subjects but spontaneous in vitro synthesis of RF occurs only in rheumatoid arthritis (RA). The regulatory role of RF-specific suppressor T cells in this process was studied in pokeweed mitogen-stimulated in vitro cultures of peripheral blood mononuclear cells. Addition of graded numbers of suppressor T8(+) cells from RA patients to normal B cells resulted in consistently less suppression of IgM and RF synthesis than that achieved by normal suppressor T cells. A preculture system was then used to probe for RF-specific suppressor precursor lymphocytes. RA T-cell populations failed to generate normal levels of RF-specific suppression during in vitro culture for 4 days. Incubation with human-aggregated IgG (HaIgG) resulted in an increase in RF-specific suppression to normal levels. The data indicate that induction and full expression of RF-specific suppressor T-cell function is blocked in vivo in RA but can be overcome in vitro by incubation with HaIgG.