TNF and B cell deficiency: B cell deficiency results in the reduction of TNF‐α‐producing M1 macrophages in EAT,14 and transfer of EAT B2 cells from HFD‐fed wild‐type mice to HFD‐fed Bnull mice leads to an increase in M1‐like macrophages.15 In vitro, EAT B cells from HFD‐fed mice promote expression of TNF‐α, IL‐6 and IL‐1β in M1 macrophages.15 Our results showed that MAT B lymphocytes isolated from HFD‐fed mice elevated the pro‐inflammatory cytokine secretion of macrophages and promoted their differentiation to type I macrophages.