Irradiated and Preserved Leukocytes in Mixed Leukocyte Cultures. ∗

Abstract

Summary and conclusions

When leukocytes received 1,5-00 r or more in vitro, they were rendered incapable of DNA synthesis and mitosis in mixed leukocyte cultures, but did not lose their ability to stimulate the blastogenesis of allogeneic intact leukocytes. The sum of the “one-way” (Ax + B) and (A -f- Bx) reactions was approximately equal to the “two-way” (A + B) reaction. Therefore, irradiated leukocytes can be used for unidirectional quantitation of the mixed leukocyte reaction. When leukocytes were irradiated with less than 6,000 r and cultured with PHA, some transformation to blasts occurred. Leukocytes stored at —70°C for 2 weeks retained their capacity for blast transformation when cultured in the presence of X-irradiated allogeneic cells. Frozen storage of irradiated leukocytes reduced their blas-togenic effect variably up to 30% of that of fresh controls.