Naturally-occurring anti-alpha-galactosyl antibodies in human Plasmodium falciparum infections--a possible role for autoantibodies in malaria.

Naturally-occurring antibodies with a distinct alpha-galactosyl specificity (anti-gal) have been earlier implicated in opsonization and elimination of human senescent erythrocytes from circulation. In the present study a cell-ELISA was developed for quantification of anti-gal antibodies in human sera. Using the test, titres of anti-gal were found to be significantly elevated in many of the sera collected from subjects living in malaria endemic areas or patients with acute Plasmodium falciparum malaria, in comparison to the titres in subjects living in areas where the incidence of P. falciparum malaria was scarce. IgG subclass typing by cell-ELISA revealed IgG3 to be the predominant type with anti-gal activity in P. falciparum infected patients' serum while IgG2 was found to be dominant in the non-endemic control serum. These findings appear to have implications in P. falciparum malaria, since putative antigens with alpha-galactosyl determinants have been identified in the erythrocytic stage parasites of P. falciparum.