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.
Pathogenicity due to secreted exotoxin. Airborne infection, nasopharyngeal tract. Exotoxin forms a membrane out of fibrin, white blood cells, dead epithelial cells, which causes suffocation. Kills 3 million people a year. Reemerged in the '90 in the inner cities with strains resistant to antibiotics.