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 alpha 4 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 alpha 4 and beta 1 integrins showed consistent, low revels of expression. Although alpha 4 was expressed at lower levels on neutrophils than all other rat leukocytes, this level of expression was sufficient to mediate significant levels of alpha 4- and beta 1-dependent neutrophil adhesion to rat and human VCAM-1, and alpha 4-dependent, but beta 1-independent, adhesion to human MAdCAM-1. These data suggest that rat neutrophils, unlike other species, may use alpha 4 integrins to traffic to sites of inflammation in vivo. (C) 1998 by The American Society of Hematology.