In vitro responsiveness of lymphocytes of different mouse strains to phytohaemagglutinin.

: Responsiveness of spleen and lymph node lymphocytes to in vitro stimulation by phytohaemagglutinin was investigated in several mouse strains. Considerable interstain differences in RNA and DNA synthesis were found both for PHA-stimulated and unstimulated cells; the latter component thus tends to contribute to the observed over-all differences in lymphocyte responsiveness to "specific" stimulation. Of the tested strains and F-1 HYBRIDS, THE HIGHEST RESPONDERS WERE A/Ph, its F-1 hybrids with a few other strains and BALB/C. The possibility that the interstrain differences in the rate of nucleic acid synthesis and hence in lymphocyte responsiveness could be due to different sensitivity of the lymphocytes to experimental treatment was not confirmed experimentally. Relatively high rate of synthesis of nucleic acids in PHA unstimulated cells and its great interstrain variation is interpreted in terms of variation in "spontaneous" transformability.