CD86 and COVID-19: Human dipeptidyl peptidase 4 (DPP4) expression is higher in visceral AT and directly correlates with adipocyte inflammation and insulin resistance. DPP4 plays also an important role in immune regulation by activating T cells and upregulating CD86 expression and NF-jB pathway. DPP4 was also identified as a functional receptor for the spike protein of the Middle East respiratory syndrome (MERS)-CoV. DPP4 could also play a role in the immune response to COVID-19.