The ability of human TIM1 to bind phosphatidylethanolamine enhances viral uptake and efferocytosis compared to rhesus and mouse orthologs.

We previously reported that human T-cell Immunoglobulin and Mucin protein 1 (TIM1) binds phosphatidylethanolamine (PE) as well as phosphatidylserine (PS) and that PE is exposed on the apoptotic cells and viral envelopes. Moreover, TIM1 recognition of PE contributes to phagocytic clearance of apoptotic cells and virus uptake. Here we report that unlike human TIM1, murine and rhesus TIM1 orthologs bind only PS, and as a result, their ability to clear apoptotic cells or promote virus infection is less efficient. These findings are significant because they imply that the activity of TIM1 in humans is greater than what the studies conducted in common animal models would indicate.