Antigen Processing Pathways in Mycobacterium tuberculosis Pathogenesis and Links to Clinical Presentation

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen that has co-evolved with humans and developed various decoy strategies to survive in hostile environments by manipulating host immunity to its advantage. This occurs through selective antigen presentation at the cellular level, induction of dysfunctional immune responses, and a clinical latency period that hampers active surveillance of disease transmission. The spectrum of clinical symptoms is a function of immune responses and may, but does not necessarily, correlate directly with disease burden. This chapter will explore the biology of Mycobacterium tuberculosis, focusing on selected genes and their products that are crucial in host-pathogen interactions, which subsequently result in the clinical presentation of tuberculosis (TB). It will look at the bacilli’s intracellular location, its antigens’ release and presentation, their processing pathways, immune responses, and granuloma formation. Both pulmonary and extrapulmonary clinical presentations are presented, including the destructive role of inflammation in the disease. The chapter will also briefly mention Mtb genes used in rapid clinical diagnostics and the role of selected TB antigens in the design of new vaccines.