T-cell macrophage subset interactions and decreased autologous mixed lymphocyte reaction in Sjögren's syndrome.

T-cell macrophage subset interactions were studied in relation to the decreased autologous mixed lymphocyte reaction (AMLR) in 15 patients with Sjögren's syndrome (SS). Monoclonal antibodies against a macrophage (M theta) subset (Mac-120) stimulatory in the AMLR and against nonpolymorphic determinants of Ia antigen were used to identify adherent M theta. Four patients with decreased AMLR had a reduced percentage of Mac-120+ cells, suggesting that a defect in stimulatory M theta may account for their decreased AMLR. No correlation was found between the magnitude of the AMLR and the percentage of Ia+ M theta. Another six patients with diminished AMLR had a normal to high percentage of Mac-120+ M theta. However, this group of SS patients showed a decreased response to Concanavalin A, suggesting that they may have a defect in the responding T cells. Patients with normal AMLR had normal percentages of Mac-120+ M theta and showed normal responses to T-cell mitogens and alloantigens. These results suggest that a defective AMLR may have multiple causes. SS patients are heterogeneous in this regard and can be sorted into three groups using the AMLR and monoclonal antibodies.