B7H4 is a co-stimulatory protein though to function as a negative regulator of T-cell mediated immunity by blocking proliferation, cell cycle progression and interleukin-2 (IL-2) production. Because B7H4-deficient mice are only minimally affected, it appears that B7H4 is involved in fine tuning of the T-cell mediated immune response. B7H4 is expressed on activated T-cells, B-cells, monocytes, and dendritic cells and exists in three different isoforms.
