IgM in human immunity to Plasmodium falciparum malaria.

Most studies on human immunity to malaria have focused on the roles of immunoglobulin G (IgG), whereas the roles of IgM remain undefined. Analyzing multiple human cohorts to assess the dynamics of malaria-specific IgM during experimentally induced and naturally acquired malaria, we identified IgM activity against blood-stage parasites. We found that merozoite-specific IgM appears rapidly in Plasmodium falciparum infection and is prominent during malaria in children and adults with lifetime exposure, together with IgG. Unexpectedly, IgM persisted for extended periods of time; we found no difference in decay of merozoite-specific IgM over time compared to that of IgG. IgM blocked merozoite invasion of red blood cells in a complement-dependent manner. IgM was also associated with significantly reduced risk of clinical malaria in a longitudinal cohort of children. These findings suggest that merozoite-specific IgM is an important functional and long-lived antibody response targeting blood-stage malaria parasites that contributes to malaria immunity.

Malaria and immunity during pregnancy and postpartum: a tale of two species.

It is well established that pregnant women are at an increased risk of Plasmodium falciparum infection when compared to non-pregnant individuals and limited epidemiological data suggest Plasmodium vivax risk also increases with pregnancy. The risk of P. falciparum declines with successive pregnancies due to the acquisition of immunity to pregnancy-specific P. falciparum variants. However, despite similar declines in P. vivax risk with successive pregnancies, there is a paucity of evidence P. vivax-specific immunity. Cross-species immunity, as well as immunological and physiological changes that occur during pregnancy may influence the susceptibility to both P. vivax and P. falciparum. The period following delivery, the postpartum period, is relatively understudied and available epidemiological data suggests that it may also be a period of increased risk of infection to Plasmodium spp. Here we review the literature and directly compare and contrast the epidemiology, clinical pathogenesis and immunological features of P. vivax and P. falciparum in pregnancy, with a particular focus on studies performed in areas co-endemic for both species. Furthermore, we review the intriguing epidemiology literature of both P. falciparum and P. vivax postpartum and relate observations to the growing literature pertaining to malaria immunology in the postpartum period.

Incidence of diagnosed deep vein thrombosis in the general population: systematic review.

OBJECTIVE: to determine the incidence of deep vein thrombosis (DVT) in the general population by pooling results from all studies of adequate quality. DESIGN: systematic review including meta-analysis. MATERIAL AND METHODS: MEDLINE (1966-2001) and EMBASE (1950-2001) were searched for studies on the incidence of DVTand thromboembolism in the general population. Studies had to attain minimum inclusion and quality criteria to be accepted for the review, including adequate specification of the diagnosis of DVT and the age range of the population. The appraisal of studies for inclusion and abstraction of data were carried out independently by each author. Incidence rates were adjusted to standardise for differences between studies in categories of DVT and population age structures. Weighted and unweighted means of incidence per 10 000 person years were estimated. RESULTS: nine studies were identified which fulfilled the inclusion and quality criteria. Most were conducted in Sweden or U.S.A. between 1976 and 2000. The weighted mean incidence of first DVT in the whole general population was 5.04 (95% CI 4.70, 5.38) per 10 000 person years. The incidence was similar in males and females and increased dramatically with age from about 2-3 per 10 000 person years at age 30-49 to 20 per 10 000 person years at age 70-79. Around 40% of cases of DVT were idiopathic. CONCLUSION: this study provides the most comprehensive estimate to date of the incidence of DVT in the whole general population-around 5 per 10 000 per annum-and is a useful background figure for comparison with incidence in high risk groups.