A 24-year-old woman presents with a 3-day history of fever and cough with rust-colored sputum. He had splenectomy 1 year ago. CXR film indicates consolidation of right lower lobe. Blood cultures are positive for alpha hemolytic gram-positive diplococci. Immunity to the causative organism is based on
Alternative complement pathway activation Antibody to fimbriae IgA antibodies to C carbohydrate IgG antibodies to a surface acidic polysaccharide