Stimulation of autoantibody production in normal blood lymphocytes by malaria culture supernatants.

Supernatants from Plasmodium falciparum cultures containing soluble parasite material were mitogenic for normal human peripheral blood mononuclear cells (MNC) in vitro. This was evidenced by blast transformation and significant incorporation of 3H-thymidine and confirms earlier reports of the mitogenic potential of malaria parasites. Lymphocyte activation by these malaria derived products was polyclonal as demonstrated by increased secretion of IgA, IgG and IgM by the stimulated cells. Using rat tissues and Hep-2 cells as substrates, autoantibody activity was found in the IgM fraction of the secreted immunoglobulin. Speckled anti-nuclear (ANA) antibody, anti-globulins (rheumatoid factor) and anti-intermediate filament antibodies were produced by the stimulated lymphocytes. No significant immunoglobulin secretion with autoantibody specificity was found in control cultures in which normal MNC were incubated with supernatants from non-parasitized red cell cultures. The data supports the suggestion that polyclonal lymphocyte activation by parasite derived products occurs in vivo and, in addition, provides an explanation for the presence of autoantibodies in the serum of malaria patients.