ANPEP and infection: To differentiate whether the A. phagocytophilum-CD13 interaction that promotes infection occurs through bacterial engagement of the CD13 C-terminus or if it requires CD13 ectopeptidase activity, promyelocytic HL-60 cells were treated with antibodies against CD13 C-terminal amino acids 781–967 (CD13781–967) or the CD13 enzymatic neutralizing antibody, WM15.