Imbalanced distribution of IgM and IgG antibodies against Plasmodium falciparum antigens and merozoite surface protein-1 (MSP1) in pregnancy.

In malaria endemic areas, pregnancy is assumed to be associated with a specific reduction in immunity to Plasmodium falciparum malaria. To understand some of the mechanisms which underlie such a poor immunity, we have attempted to examine the frequency and distribution of IgM and IgG antibodies to a crude antigenic extract of parasitized erythrocytes and to the merozoite surface protein-1 (MSP1), in a population of mothers compared to control non-pregnant women, all living in Dakar and suburbs. Specifically, this work describes: (i) the responses of mothers and control women; (ii) the balance between IgM and IgG responses; and (iii) responses to malarial antigen and to MSP1. An unexpected balance between P. falciparum-specific IgM and IgG is shown, associated with a substantial increase in anti-MSP1 IgM, and a decrease in anti-MSP1 IgG in parturients.