Activation of components of the alternative pathway of complement by Propionibacterium acnes cell wall carbohydrate

The trichloroacetic acid (TCA) extractable molecules in Propionibacterium acnes cell wall were tested for the ability to activate the alternative pathway of complement in human serum treated with ethyleneglycol-bis (beta-aminoethyl ether) N,N-tetracetic acid (EGTA). The extracted molecules failed to consume hemolytic activity against antibody-coated sheep erythrocytes but gave a dose-dependent consumption of rabbit erythrocyte (RE) lytic activity. Similarly, the extract produced significant cleavage of Factor B, but failed to cleave C3, as detected by immunoelectrophoresis. Adsorption of the extracted material to sheep erythrocytes did not render the cells susceptible to lysis via the alternative pathway. Sephadex G-25 chromatography yielded several fractions which were able to consume RE lytic activity from EGTA-treated serum. These fractions were analyzed and found to contain glucose, mannose, and galactose. No teichoic acid or protein was detected. The alternative pathway activator in P. acnes is thus a nonteichoic acid cell wall carbohydrate which, in its extractable form is capable of activating only alternative pathway reactants prior to C3.