M. tuberculosis replicates in an unchecked fashion within the alveoli and alveolar macrophages due to virulence factors (cord factor) that prevent macrophage-mediated phagolysosome destruction. After a few weeks, macrophages infected display antigen on MHC II to stimulate T CD4+ cells which leads to an increase in interferon-y (Th1 cytokine) that active macrophages. Activated macrophages can also differentiate into epithelioid histiocytes and coalesce into multinucleated Langhans giant cells that wall off extracellular mycobacteria within granulomas.
In most individuals infected with M. tuberculosis, mononuclear cells in the blood release interferon-gamma when stimulated with antigens derived from M. tuberculosis.
how i remember it for all granulomas
formed by...IFN gamma
Maintained by TNF alpha
Gamma forms alpha maintains (sustains it). That is why infliximab and etarnacept( TNF alpha inhibitors) will break down the granuloma if used.