Which hypersensitivity reaction is associated with tubercular caseous necrosis?

Tubercular caseous necrosis is primarily associated with a Type IV hypersensitivity reaction. This type of hypersensitivity is also known as delayed-type hypersensitivity, which is mediated by T-helper cells and involves the activation of macrophages. In response to Mycobacterium tuberculosis, the immune system mounts a cell-mediated response characterized by the accumulation of macrophages and lymphocytes at the site of infection.

The cause of the caseous necrosis observed in tuberculosis is due to the formation of a granuloma, which is a collection of inflammatory cells including macrophages that transform into multinucleated giant cells. The central area of the granuloma can undergo necrosis, leading to the characteristic cheese-like (caseous) appearance. This pathological finding is a direct result of the immune system's attempt to wall off and contain the infection, highlighting the role of cell-mediated immunity in combating intracellular pathogens like tuberculosis.

Type I hypersensitivity typically involves an immediate allergic response mediated by IgE and mast cells, which does not correlate with caseous necrosis. Type II hypersensitivity is primarily antibody-mediated and involves cytotoxic reactions against cells, while Type III hypersensitivity involves immune complex deposition leading to acute inflammation, none of which are characteristic of the response seen in tuberc