Figure 2.

Human tuberculosis (TB) granulomatous inflammation.

Haematoxylin and eosin staining of a lung nodule that cultured Mycobacterium tuberculosis (Mtb). The typical granuloma in the centre is an organised structure of activated macrophages, T cells, and fibroblasts. Star indicates central caseous necrosis; arrowheads indicate a ring of epithelioid macrophages. However, much of the surrounding inflammation is much more poorly organised than typically represented in schematics, and the concept of individual spherical granulomas being the source of TB cavities is being challenged.