CRP is a protein seen in ceain systemic inflammatory conditions. Here 'C' stands for:

C-reactive protein (CRP, so named because it reacts with the C polysaccharide of pneumococci) is an acute phase protein. It can stimulate the classic complement pathway. CRP is used as a marker of tissue injury, infection, and inflammation, and there is considerable interest in its use as a predictor of ceain types of cardiovascular conditions secondary to atherosclerosis. Ref: Murray R.K., Jacob M., Varghese J. (2011). Chapter 50. Plasma Proteins & Immunoglobulins. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.