['To investigate cellular immune responses to streptococcal antigens in patients with psoriatic arthritis (PsA). To specifically examine responses of the gamma delta + T cell subset.', 'Proliferation of PsA synovial fluid lymphocytes (SFL) and peripheral blood lymphocytes (PBL) cultured with streptococcal antigen was measured using a 3H thymidine (3HTdr) uptake assay system. gamma delta + T cells from PsA PBL and SFL were phenotyped by flow cytometry. Following culture with streptococcal antigen, gamma delta + enriched SFL were sorted by automated flow cytometry and 3HTdr uptake measured.', 'Patients with PsA and the control group did not differ significantly in their PBL responses to 2 strains of streptococci, one of which was isolated from a patient with guttate psoriasis (Strep 1) and the other from a patient with rheumatic fever (Strep 2). There was also no difference in their responses to a cell wall preparation derived from the former strain. SFL from 8 of 9 patients with PsA responded to both streptococcal strains as did SFL from 3 patients with rheumatoid arthritis (RA). gamma delta + SFL from 7 patients with PsA 3 patients with RA responded only to the psoriasis associated strain.'] Do gamma delta + T cells from patients with psoriatic and rheumatoid arthritis respond to streptococcal antigen?