Secretory IgA blocks attachment to mucosal epithelial cells. Abs can activate the complement, and act as opsonizing Abs. Inside there are 8 different strands of ssRNA and a RNA polymerase. Antigenic drifts caused by spontaneous point mutations result in minor changes and are actually due to selection by Abs. Also, from 95 on the H1N1 reappeared in Texas.
Abs are important to protect from reinfection with the same strain.
Abs are bypassed by Ag drift. A crossreactive Ag is the nucleoprotein. Abs against extracellular bacteria and DTH against intracellular bacteria. Chlamydia blocks lysosomal fusion with phagosomes. Mycobacteria are resistant to oxidative attack in phagolysosomes.