Defective in vitro production of anti-Plasmodium falciparum antibodies in some malaria-immune subjects

The cell requirements for immunoglobulin (Ig) and Plasmodium falciparum-specific antibody production in the presence of schizont-enriched malaria antigen (M.Ag) were studied in vitro. Cell donors were healthy immune adult Africans and Europeans who had experienced single P. falciparum acute infection. In the presence of M.Ag a dose-dependent increase in polyclonal IgM and IgG levels was observed with T/B cell cultures from 4/4 European and from 4/14 African donors (high-Ig producers). In 10/14 Africans M.Ag failed to induce significant Ig production (low-Ig producers). No differences in Ig levels between high- and low-Ig producers were observed in the presence of pokeweed mitogen (PWM). The addition of CD8+T cells to CD4+T/B cell cultures significantly suppressed the Ig production in PWM- but not in M.Ag-activated cultures. High levels of P. falciparum-specific antibodies were found in M.Ag-activated cultures from high-Ig producer Africans but not in cultures from Europeans or from low-Ig producer Africans. The in vitro production reflected differences in plasma levels of specific antibodies.