Effect of calf thymus histone and its fractions F2 and F3 on human lymphocyte stimulation by phytohaemagglutin.

The effect of exogenous calf thymus histone and its fractions F2 and F3 on blastic transformation of human lymphocytes stimulated by phytohaemagglutinin was investigated. It was found that histones can not only inhibit, but also potentiate phytohaemagglutinin-induced blastic transformation of lymphocytes. This effect depends on the amount of histones in the medium and most probably also on individual sensitivity of lymphocytes. The arginine-rich histone fraction (F3) displayed the greatest inhibitory effect on lymphocyte stimulation.