RELATIVE CONTRIBUTION OF CELL-WALL AND CAPSULAR POLYSACCHARIDES IN ACTIVATING ALTERNATIVE AND CLASSICAL COMPLEMENT PATHWAYS BY STREPTOCOCCUS-PNEUMONIAE

Pneumococcal cell wall polysaccharide vigorously activated the alterna tive complement pathway as shown by generation of factor Bb; capsule w as responsible for a further increase of Bb generation ranging from 27 % to 77%. Activation of the classical pathway was largely determined b y anti-cell wall polysaccharide antibody that is ubiquitous in normal human serum. These findings help to explain the capacity of pneumococc i to generate a vigorous inflammatory response in the non-immune host.