Abnormalities of peripheral blood lymphocytes in rheumatoid arthritis.

Peripheral blood lymphocytes from some rheumatoid arthritis (RA) patients show a reduced response to PHA when stimulated directly after isolation from blood. Cells which have been preincubated in medium with normal serum for 22 h before exposure to PHA show a relatively enhanced response, which approximates the normal. These findings could be compatible either with the blocking of surface PHA receptors of circulating RA lymphocytes, or with progressive maturation of these cells in vitro. Preincubation does not enhance the relatively reduced response of RA lymphocytes to allogeneic RA lymphocytes in one-way mixed lymphocyte cultures. An increased reduction in response to PHA following irradiation of RA lymphocytes suggests an increased radiosensitivity of the PHA-responsive subpopulation. This abnormally reduced response was not seen if the cells were preincubated in vitro prior to irradiation.