S100A9 and Granuloma: Furthermore, neutrophils expressing S100A9 (a calcium-binding protein of the S100 family, related to neutrophil extravasation and macrophage activation functions) have been associated with granuloma formation, as shown by abundant levels of S100A9+ neutrophils in the central area of granulomas in a guinea pig model of pulmonary TB, and in humans (Yoshioka et al., 2016).