Some functional properties of the RNP nucleoplasmic antigen.

The effect of nuclear stimulators and inhibitors on the nuclear contents of nucleoplasmic antigens (ENA) was studied by the indirect immunofluorescence technique. Human autoimmune sera, one reacting with RNase-A-sensitive and one with RNase-A-resistant components of ENA in the passive haemagglutination test, were used as indicators of the RNP and Sm antigens, respectively. Phytohaemagglutinin and concanavalin A both caused an accumulation of these antigens in normal blood lymphocytes. With pokeweed mitogen, staphylococcal protein A, or purified protein derivative the accumulation was apparently restricted to B cells, alpha-amanitine, 10 microgram/ml, prevented the mitogen-induced accumulation of RNP in normal human blood lymphocytes and reduced the contents of this antigen in several lymphoblastoid cell lines and in HeLa cells but did not significantly affect the contents of Sm antigen in any of these cell types. The experimental results suggest that the RNP and Sm nucleoplasmic antigens are normal rapid-phase reactants integrated in physiological nuclear mechanisms rather than inert structural constituents of the nuclear matrix or the products of a latent virus.