IgG₁ hypergammaglobulinaemia in chronic parasitic infections in mice: Evidence that the response reflects chronicity of antigen exposure

The IgG₁ molecules in the sera of IgG₁ hypergammaglobulinaemic mice chronically infected with the larval cestode, Mesocestoides corti, are a heterogeneous population. Although antibodies to M. corti are present, the question of whether a minority or majority of the serum IgG₁ molecules has anti-parasite reactivity remains open. The splenic PFC response to an intravenous injection of SRBC in M. corti-infected mice does not consist of an unusually high proportion of IgG₁ anti-SRBC PFC. Moreover, the adoptive anti-DNP PFC response of spleen cells from M. corti-infected mice to DNP-M. corti is not biased towards IgG₁ antibody production. Since IgG₁ hypergammaglobulinaemia is seen in mice with chronic, 'high-dose' infections, an attempt has been made to simulate chronic antigenic exposure with SRBC in uninfected mice. A split, high'dose regime of SRBC injections leads to a high number and high proportion of IgG₁ anti-SRBC PFC in the spleen in three strains of mice. The results suggest that the extra-ordinarily high levels of IgG₁ seen in the sera of mice chronically infected with the metazoa, M. corti and Nematospiroides dubius, reflect persistent, high-dose, 'strong', T cell-dependent stimulation of the B cell system.