<prompt> C in C-reactive protein stands for:Capsular polysaccharide of S. pneumoniaeConcanavalin-ACalretininCellular  <response>: Ans. a Capsular polysaccharide of S. pneumoniae Ref. Ananthanarayan 8e, p 221, 9e 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. 