IgE antibodies are more species-specific than IgG antibodies in human onchocerciasis and lymphatic filariasis.

To explore the relative species specificities of the IgE and IgG antibody responses to helminth infections in man, we studied four pools of sera from patients infected with Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus or Ascaris lumbricoides and ten individual sera from patients with onchocerciasis. IgE antibodies were detected by radioallergosorbent test (RAST) analysis and IgG antibodies by a Staphylococcus protein A radioimmunoassay (Staph A-RIA). Analysis of the binding curves with four different immunosorbents (prepared from antigens of B. malayi, O. volvulus, Dipetalonema viteae and A. lumbricoides) in the RAST and the binding curves with these same four antigens in the Staph A-RIA confirmed the relative species specificities for both the IgE and IgG antibody responses. Then determination of these antibody levels after specific absorption of the sera with both homologous and heterologous antigens showed that in all instances there was significantly less cross-reactivity with heterologous parasite antigens (i.e. higher species specificity) in the IgE antibody response to filarial infection than in the corresponding IgG antibody response. Such findings imply that efforts toward developing techniques for specific immunodiagnosis of filarial infections are likely to be particularly successful if focused on the IgE antibody response of exposed individuals.