Blastogenesis of rhesus peripheral lymphocytes with competitive summation of PHA and ALS responses

Rhesus monkey peripheral lymphocytes were found to undergo consistently high levels of PHA- and ALS-induced blastogenesis when in optimum culture conditions. For mitogen-induced lymphoblastogenesis, the culture conditions were defined in terms of continuous agitation incubation, cell density and serum content of the medium. The simultaneous measurement of blastogenic responses by autoradiographic and liquid scintillation methods established a linear relationship from which the percentage of responding lymphocytes could be derived from the total thymidine incorporation levels. Phytohaemagglutinin (PHA) and heterologous anti-lymphocyte sera (ALS) induced similar proliferation kinetics and maximal blastogenic responses under these culture conditions. Optimum stimulating concentrations of both mitogens in the same cultures produced no summation of their individual blastogenic responses; however, summation occurred at suboptimal mitogen doses. PHA and ALS appeared to be mitogenically stimulating the same lymphocyte population. Furthermore, no competitive inhibition was evident during simultaneous stimulation, suggesting that their induction events were neither additive nor competitive.