Abstract
Some of the conditions and parameters of the proliferative response in the mixed lymphocyte interaction have been studied with the use of culture inocula consisting of lymphoid cells from various immunogenetically diverse, isogenic strains of rats. Procedures are described by which consistent culture responses can be obtained which are measurable in terms of incorporation of radioactive thymidine into a trichloroacetic acid precipitable cell fraction. Results of experiments with this "mixed lymphocyte interaction" show that