C in C-reactive protein stands for:

Ans. (a) Capsular polysaccharide of S. pneumoniae Ref. Ananthanarayan 8/e, p 221, 9/e p 225 'C' Reactive protein An abnormal protein (beta 1 globulin) that precipitates with the somatic 'C' antigen of pneumococci, appears in the acute phase of pneumonia and disappears during convalescence. This protein found in other conditions also is called as C-reactive protein, where C stands for the C substance of pneumococci. This C-RP is not an antibody, rather a acute phase reactant synthesised in liver in response to bacterial infection, inflammation. What is C substance? Cell wall of pneumococci contains two types of teichoic acid; one exposed on the cell surface and the other similar form covolently bound to membrane lipids. The exposed teichoic acid is referred as 'C' substance. This 'C' substance is common to all pneumococci and is unrelated to the group specific carbohydrate of 13 hemolytic streptococci. Remember: Pneumococci has three antigenic determinants: - Capsular polysaccharide - Somatic M protein - Cell wall carbohydrate So it is clear that 'C' does not stands for any of the choice mentioned in question, as only option 'a' relates it to pneumococci it can be taken as correct answer.