Malaria parasitemia and systemic cytokine bias in pregnancy.

OBJECTIVES

To investigate the effects of age, gravidity, and gestational age on peripheral malaria parasitemia and functional T helper (Th) cell heterogeneity in pregnant women.

METHODS

Maternal age, gravidity, and gestational age were recorded and peripheral venous blood collected from 175 women attending antenatal clinics in south western Cameroon between March and September 2002. The blood was checked for malaria parasitemia by light microscopy and plasma levels of interleukin (IL)-4 and human interferon (IFN)-gamma were measured by indirect enzyme-linked immunosorbent assay.

RESULTS

Malaria parasites were detected in 45 (25.4%) of 174 women, with rates similar for different age groups, trimesters of pregnancy, and gravidity. The geometric mean parasite density was 565, and parasite density was significantly higher in younger than in older women. For all groups combined, the mean IL-4 level was significantly higher than the mean IFN-gamma (P=0.0004), irrespective of the presence and density of malaria parasites, gravidity except for women in their first trimester of pregnancy and grandmultiparas, who had similar levels of IFN-gamma and IL-4. In general, the cytokine profile was biased toward Th2-type of responses in 112 (84.3%) of 132 women.

CONCLUSIONS

In this study the ability to control malaria parasitemia during pregnancy was found to be predominantly age dependent, suggesting naturally acquired immunity. Furthermore, the systemic cytokine profile was found to be biased towards Th2 responses, a prerequisite for a successful pregnancy. This pattern was unaffected by maternal age, gestational age, gravidity, or parasitemia.