Anti-filarial IgG4 in men and women living in Brugia malayi-endemic areas.

To assess whether antifilarial IgG4 can be used to study various epidemiological facets of filarial infections, we studied this isotype in 238 individuals resident in areas endemic for brugian filariasis, focusing on the differences between men and women. In the study area, the prevalence of microfilariae was 6.7% and the prevalence of antifilarial IgG4 was 49.2%. All microfilariae carriers were positive for antifilarial IgG4, whereas a proportion of the endemic normals (94/208) and clephantiasis patients (7/14) had IgG4 antibodies to filarial antigens. Data were analysed as a function of gender in distinct clinical groups and stratified for age. The prevalence of microfilariae was higher in males in all age groups, as reflected in significantly higher antifilarial IgG4 antibody levels compared to females. The prevalence of IgG4 increased to reach a plateau at the age of 30 years in both males and females. These results indicate that antifilarial IgG4 antibodies can reflect the differences in the extent of infection in males and females as measured by microfilarial counts, and that this parameter can be used for epidemiological assessments of filarial infection.