IGG SUBCLASSES IN HUMAN HYDATID-DISEASE - PROMINENCE OF THE LGG4 RESPONSE

To assess the participation of the four subclasses of IgG in the humor al response to Echinococcus granulosus infection, we determined total and parasite-specific IgG1, IgG2, IgG3 and IgG4 in sera from 46 patien ts with hydatid disease using an enzyme-linked immunosorbent assay (EL ISA). Parasite-specific IgG subclass antibodies were quantitatively me asured by means of standard curves obtained by affinity chromatography . Sera from 35 healthy individuals served as controls. The total compo nent of IgG1, IgG2, and IgG3 showed a slight increase in patients with hydatidosis in comparison to normal control subjects with no signific ant differences. For the IgG4 subclass, however, a marked elevation wa s found in the patients group (p = 0.001 by analysis of variance). IgG 1 and IgG4 subclasses showed a high anti-echinococcus antibody respons e, whereas there was a low parasite-specific IgG2 and IgG3 response. I ndeed IgG-specific antibodies were found to belong mainly to IgG1 (63% ) and to IgG4 (30%) and to a lesser extent to IgG2 (5%) and IgG3 (2%). The percentage of the total serum IgG4 antibodies that were specific for hydatid antigen reached a mean level of 18%, significantly higher than that of any of the other three IgG subclasses (p < 0.001 by Stude nt's t test). Thus, the continuous antigenic stimulation of hydatidosi s may result in an enhanced IgG4 subclass response.