Rat Neutrophils Express α4 and β1 Integrins and Bind to Vascular Cell Adhesion Molecule-1 (VCAM-1) and Mucosal Addressin Cell Adhesion Molecule-1 (MAdCAM-1)

The α4 integrins, which are constitutively expressed on all human leukocyte subtypes except neutrophils, interact with vascular cell adhesion molecule-1 (VCAM-1) and mucosal addressin cell adhesion molecule (MAdCAM-1) on endothelium to mediate selective recruitment of leukocyte subpopulations, other than neutrophils, to sites of inflammation. However, here we report that a different paradigm of leukocyte recruitment may exist in the rat. Flow cytometric analysis of rat neutrophils using a panel of monoclonal antibodies which recognize rat α4 and β1 integrins showed consistent, low levels of expression. Although α4 was expressed at lower levels on neutrophils than all other rat leukocytes, this level of expression was sufficient to mediate significant levels of α4- and β1-dependent neutrophil adhesion to rat and human VCAM-1, and α4-dependent, but β1-independent, adhesion to human MAdCAM-1. These data suggest that rat neutrophils, unlike other species, may use α4 integrins to traffic to sites of inflammation in vivo.