Experimental antigen-antibody complex disease in mice. The role of antibody levels, antibody affinity and circulating antigen-antibody complexes.

Abstract:  Chronic antigen-antibody complex disease (A-ACD) was induced in mice by daily injections of HSA. The disease was characterized by death, intense glomerular basement membrane deposition of complexes in the kidneys, proteinuria and an impairment of the glomerular filtration rate. In mice that had been selectively bred to produce antibody of low affinity to protein antigens injected in saline, the incidence of chronic A-ACD was 61% compared to 21% in mice selectively bred to produce antibody of high affinity. Low affinity female mice produced approximately ten times as much free antibody to HSA as did low affinity males and high affinity males and females, but this did not result in an increase incidence of chronic A-ACD in low affinity female mice. Low affinity female mice also had the highest levels of circulating antigen-antibody complexes detected by conglutinin and Clq binding assays, but there was no correlation between the presence of high levels of complexes in serum and tissue damage. In both lines of mice the mean affinity of free antibody to HSA started low and increased with time and the number of injections of antigen. However, development of chronic A-ACD in individual low affinity mice appeared to be associated with a failure to produce this time-associated increase in antibody affinity. These results are discussed with reference to the relevance of the measurement of the amount of affinity of free antibody in serum and the levels of circulating antigen-antibody complexes to the production of tissue damage in this model of chronic A-ACD.