Activation of the alternative pathway of complement in human serum by Propionibacterium acnes (Corynebacterium...

Activation of the alternative pathway of complement is known to be initiated by bacterial structures. We have fractionated Propionibacterium acnes cells, purified various cell fractions, and tested their complement-activating ability in human serum chelated with ethyleneglycol bis-(beta-aminoethylether)-N,N1-tetraacetic acid. The majority of complement-activating activity was localized in the wall fraction. This activity was resistant to lipid extraction, protease, RNAse, DNAse and lysozyme treatment. NaIO4, formamide, and hot (but not cold) trichloroacetic acid (TCA) extraction ablated the complement-activating capacity of cell walls. Compounds removed by extraction failed to consume significant hemolytic activity against antibody-coated sheep erythrocytes (EA). Addition of TCA-extracted soluble material to cell wall suspensions resulted in an inhibition of hemolytic consumption by the cell wall. These results indicate that, in P. acnes, complement-activating molecules are located in the cell wall and are carbohydrate in nature. Peptidoglycan, lipid, protein, and nucleic acid do not appear to contribute to the cell wall's ability to activate complement.