Inhibition of synovial fluid T cell proliferation by anti-CD5 monoclonal antibodies. A potential mechanism for their immunotherapeutic action in vivo.
OBJECTIVE
Monoclonal antibodies (MAb) directed against the T cell surface molecule CD5 are able to provide accessory stimulatory signals to resting T cells. The potential role of CD5 as an immunoregulatory molecule in inflammatory synovitis was examined.


METHODS
Synovial fluid and peripheral blood T cells of patients with active rheumatoid arthritis (RA) were purified and stimulated with interleukin-2 (IL-2), and the effect of MAb directed against CD5 on IL-2 responsiveness was examined.


RESULTS
IL-2-induced proliferation of synovial fluid T cells was strongly inhibited by anti-CD5 MAb, but not by anti-CD28 or anti-CD3 MAb. In RA peripheral blood T cells, MAb directed against CD5, CD3, and CD28 induced IL-2-dependent T cell growth, similar to findings in healthy controls. The difference in activity of anti-CD5 MAb on synovial fluid T cells compared with peripheral blood T cells was not due to different surface expression of CD5.


CONCLUSIONS
Anti-CD5 has an inhibitory effect on in vivo-activated synovial fluid T cells. The disease-ameliorative effects of anti-CD5 immunotoxin treatment of RA may be partly due to "switching-off" of T cell activation in the joints.
D000328:Adult; D000911:Antibodies, Monoclonal / Q000032:analysis / Q000276:immunology / Q000494:pharmacology*; D015703:Antigens, CD / Q000032:analysis / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000473:pathology / Q000628:therapy; D018106:CD28 Antigens; D017252:CD3 Complex / Q000032:analysis / Q000276:immunology; D018956:CD5 Antigens; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002469:Cell Separation; D002478:Cells, Cultured; D005260:Female; D006684:HLA-DR Antigens / Q000032:analysis / Q000276:immunology; D006801:Humans; D007166:Immunosuppressive Agents; D007167:Immunotherapy; D007376:Interleukin-2 / Q000494:pharmacology; D008297:Male; D015375:Receptors, Interleukin-2 / Q000032:analysis; D013582:Synovial Fluid / Q000166:cytology*; D013601:T-Lymphocytes / Q000737:chemistry / Q000473:pathology* / Q000648:ultrastructure
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018106:CD28 Antigens; D017252:CD3 Complex; D018956:CD5 Antigens; D006684:HLA-DR Antigens; D007166:Immunosuppressive Agents; D007376:Interleukin-2; D015375:Receptors, Interleukin-2