Reduced in vitro immune responses of purified human Leu-3 (helper/induced phenotype) cells after total lymphoid irradiation.

Patients treated with total lymphoid irradiation (TLI) for intractable rheumatoid arthritis showed marked decreases in the in vitro proliferative responses of peripheral blood mononuclear cells (PBM) to antigens and mitogens. To determine whether an intrinsic deficit in helper/inducer cell proliferation contributed to decreased responses, cells of the helper/inducer phenotype were purified from the PBM of treated patients by using monoclonal anti-Leu-3 antibody and a modified panning procedure. The purified Leu-3 cells obtained after TLI showed a marked reduction in [3H]thymidine incorporation in response to allogeneic lymphocytes, PHA, Con A, and several protein antigens, as compared with that of cells from the same patients obtained before TLI. In addition, the quantity of Leu-3 surface antigen on the panned cells was reduced after TLI. The results suggest that TLI induces prolonged qualitative as well as quantitative changes in circulating Leu-3 T cells. These changes may contribute to the clinical effects of TLI.