CD4+ T cells secrete IL-2 and interferon gamma (IFNγ), inducing the further release of other Th1 cytokines, thus mediating the immune response.

Type IV hypersensitivity can usually be resolved with topical corticosteroids and trigger avoidance.

[1] An example of a tuberculosis (TB) infection that comes under control: M. tuberculosis cells are engulfed by macrophages after being identified as foreign but, due to an immuno-escape mechanism peculiar to mycobacteria,[4] TB bacteria block the fusion of their enclosing phagosome with lysosomes which would destroy the bacteria.

After several weeks, the immune system somehow [mechanism as yet unexplained] ramps up and, upon stimulation with interferon gamma, the macrophages become capable of killing M. tuberculosis by forming phagolysosomes and nitric oxide radicals.

The hyper-activated macrophages secrete TNF-α which recruits multiple monocytes to the site of infection.