Evidence for Pseudomonas antigen in immune complexes in Pseudomonas osteomyelitis

In infections associated with immune complex disease, microbial antigens have rarely been found in the complexes. Using an enzyme-linked immunoassay, we studied the immune complexes of a patient who had hematogenous Pseudomonas aeruginosa osteomyelitis associated with palpable purpura, arthritis, and microscopic hematuria. After separation of the complexes into high and low molecular weight fractions, a 6-fold selective concentration of P aeruginosa antibody was found in the low molecular weight fraction compared with the concentration of the serum. Following disruption of immunoglobulin, the high molecular weight fraction competed with solid-phase P aeruginosa antigen for P aeruginosa antibody from another source. After successful treatment of the infection, the patient's symptoms resolved, and the complexes disappeared. These findings strongly suggest that immune complexes in this patient contained P aeruginosa antigen and antibody that may have been pathogenetic in his disease.