Guinea pigs with inherited deficiencies of complement components C2 or C4 have characteristics of immune complex disease.

Guinea pigs genetically deficient in the second (C2) or fourth component of complement (C4) generally appear healthy in contrast to humans with a C2 or C4 deficiency. However, upon investigation of these genetic deficiencies in guinea pigs for signs of dysregulation in the humoral immune system and especially autoantibodies, many complement-deficient guinea pigs (greater than 50%) had elevated levels of serum IgM and higher concentrations of anti-hapten (dinitrophenyl) antibodies as signs of polyclonally stimulated antibody synthesis. In addition, a significant number of the complement-deficient animals, on average 30%, had IgM rheumatoid factors in their sera compared with less than 1% of the normal animals. These observations, therefore, indicate that guinea pigs, genetically deficient in C2 or C4, show characteristics of immune complex disease in general.