This includes the genes coding for the counterparts for human CRP known to activate the classical pathway upon pneumococcal infection in humans, as well as the counterparts for C1R and CFB required for the activation of C3 convertase in the classical and the alternative pathways, respectively, and C4B, a component in both the C3 and C5 convertase complexes. The gene discussed is C3; the disease is pneumococcal infection.