Changes in circulating immune complex concentrations and antibody titres during treatment of Q fever endocarditis.

Serum samples from 20 patients with Q fever endocarditis were tested for the presence of circulating immune complexes to see whether their concentrations correlated with antibody titres during treatment and whether they could be used to monitor the response to antimicrobial treatment. Circulating immune complexes were found in all 20 patients. The concentrations in 15 patients correlated with either or both of the Q fever phase 1 and phase 2 antibody titres obtained during treatment. In the other five patients no correlation with the antibody titres was found. There was no association between circulating immune complex concentrations and clinical response to treatment.