Activated T cells promote the cleavage of ICAM-5 from neurons. Human T cells were either left untreated or treated with anti-CD3 plus anti-CD28 mAbs, with or without TNF or IFN-γ (50 ng/mL), and incubated with 10- to 14-day-old rat hippocampal neurons for 16 hours. The conditioned media and hippocampal cell lysates were processed for Western blotting. ICAM-5 was detected by pAbs against the ICAM-5 cytoplasmic tail (A) or ectodomains (B,C), respectively. Full-length ICAM-5 is 130 kDa (A). Vertical lines are inserted to indicate repositioned gel lanes. Both TCR- (B) and cytokine- (C) mediated activation of T cells induced the release of sICAM-5 fragments (85-110 kDa) into the culture media. The cleavage was blocked by the MMP-2/9 inhibitor II (25 μM), MMP-9 inhibitor I (25 μM), and CTT peptide (100 μM), but not by the CTT_W/A peptide (C).