The developmental biology of the syngeneic mixed lymphocyte reaction.

Overview

The syngeneic mixed lymphocyte reaction (SMLR) is the proliferative response of T lymphocytes cultured with non-T lymphocytes. Normal mouse serum supports proliferative activity in the SMLR comparable to levels observed when fetal calf serum is used. Thus, the SMLR does not appear to be a response to xenogeneic antigens. The ontogeny and senescence of the SMLR was also studied. The SMLR is impaired in mice less than 4 weeks of age but attains adult levels of activity at 4 weeks of age. The SMLR is also impaired in 24-month-old mice. These impairments were observed regardless of the source of serum used in the cultures. Finally, monoclonal antibodies have been developed which identify a subpopulation of spleen cells which respond in the SMLR. In indirect immunofluorescence these antibodies stain 50-80% of cells activated in the SMLR, but only 5-8% of spleen cells or cells activated in the allogeneic MLR. These antibodies block the proliferative response in the SMLR but do not interfere with the response to alloantigens or PHA.