Which cytokine is known to mediate granuloma formation in immune responses?

Granuloma formation is a critical immune response, particularly in defense against persistent pathogens like mycobacteria and in the context of certain autoimmune diseases. The cytokine primarily involved in mediating this process is TNF alpha.

TNF alpha is produced by activated macrophages and plays a central role in the immune system by promoting inflammation and activating other immune cells. In the context of granulomas, TNF alpha is crucial for the recruitment and activation of macrophages, which then transform into epithelioid cells and multinucleated giant cells, hallmarks of granulomatous inflammation. This cytokine also helps in maintaining the structure of the granuloma by sustaining the activation of macrophages and ensuring that they continue to respond to ongoing infections or irritants.

Although other cytokines like IFN-gamma are involved in the immune response, particularly in promoting the activation of macrophages, it is TNF alpha that is more directly associated with the consolidation and persistence of granulomatous tissue. Thus, it is essential in forming and sustaining granulomas in chronic inflammatory conditions.