Antibody responses to filarial infective larvae are not dominated by the IgG4 isotype

The humoral immune response in humans to filarial parasites is generally do minated by the IgG4 isotype, when measured by ELISA against somatic adult w orm extract. In contrast, as we report here, antibodies reactive to somatic extracts of infective larvae are more equally represented by IgG1 and IgG4 . Moreover, binding to surface exposed epitopes in immunofluorescence on la rval stages is mediated foremost by IgG1 and IgM, secondarily by IgG2 and I gG3, and very little by IgG4. Both anti-L3 surface and somatic antibodies a re strongest in elephantiasis patients, and tend to increase with age. Anti body to the L3 surface is also present in most microfilaraemic individuals who bear no detectable antibodies to the surface of the microfilarial stage . These results demonstrate that a stage- and isotype-specific response is mounted to the L3 surface which should be considered as a possible mediator of concomitant immunity in filariasis.