Expression of the HML-1 Epitope on Human Monocytes is Independent of αE Integrin mRNA

Interferon gamma (IFNγ)-mediated activation of the myelomonocytic cell line HL-60 and peripheral blood monocytes will induce expression of an epitope for the monoclonal antibody which recognizes human αEβ7 integrin, HML-1. Here, we found that the anti-human αEβ7 monoclonal antibody Ber-ACT8 did not recognize IFNγ-stimulated, HML-1 positive HL-60 cells. Culture of blood monocytes with IFNγ also induced expression of HML-1 but not Ber-ACT8 epitopes. Moreover, migration of monocytes across a monolayer of human airway epithelial cells rapidly induced expression of HML-1, with no detectable Ber-ACT8 staining. Using two different sets of primers specific for the human αE integrin gene, we were unable to detect αE mRNA within HL-60 cells or isolated monocytes by reverse transcriptase polymerase chain reaction methods. We conclude that reactivity of the HML-1 antibody for HL-60 cells and monocytes does not correspond with the expression of the αE integrin subunit, and instead detects a marker for cellular activation.