MMP9 and Stroke: This is noteworthy since, under physiological conditions, sCD137 is generated by proteolytic cleavage from the cell surface of activated lymphocytes.38, 39 An upregulated specific MMP, i.e., gelatinase B and MMP‐9, which could cause the cleavage of CD137 from the cell surface during the acute stage of stroke,40, 41 may contribute to the increased release of sCD137.