Restricted IgG isotype profiles in T. cruzi infected mice and Chagas' disease patients.

IgG2 was the predominant specific antibody isotype in mice chronically infected with Y strain Trypanosoma cruzi; IgG1 and IgG3 antibodies were absent or present only at very low levels. Isotype analyses of the acute phase of infection confirmed no early production of IgG1 or IgG3 and no failure in the switch from IgM to IgG. In vivo passive transfer studies of immune serum fractions showed protection to be associated only with the IgG2 isotype. A characteristic specific anti-T. cruzi IgG isotype profile (IgG1, IgG3, greater than IgG2, IgG4) was detected in a majority (39 of 50) of sera from Chagas' disease patients.