**14. Immune cell infiltration**

In most cases chronic excessive caloric intake eventually leads to adipocyte dysfunction, regardless of the mechanisms of adipose tissue expansion, and this is paralleled by qualitative and quantitative changes in the composition of adipose tissue at cellular level. Immune cells are of great relevance in this regard. Low-grade chronic inflammation is a major hallmark of adipose tissue in obesity, and it is now known that almost every immune cell type can be found in the adipose tissue. Total numbers of B cells, T cells, neutrophils, macrophages, and mast cells are increased in visceral adipose tissue of obese individuals. In contrast, the number of eosinophils and specific subsets of T cells—T-helper type 2 (Th2) cells and regulatory T (Treg) cells—are decreased or remained static in the adipose tissue of obese individuals [36].

Macrophages are the most abundant immune cell in the adipose tissue of obese individuals, and their recruitment and proliferation upon high-calorie feeding is generally associated with adipose tissue inflammation and insulin resistance [44–47].
