Functional characterization of the beta2 integrins

Abstract

aLp2 (CD 1 la/CD 18, LFA-1), aMp2 (CD1 lb/CD 18, Mac-1) and, aXp2 (CD1 lc/CD18, pi50, 95) are members of P2 integrins involved in leukocyte function during immune and inflammatory responses. The first part of this study, the epitope of a p2-specific antibody MEM 148 was fine mapped to the hybrid domain and it is dependent on the movement of the hybrid domain upon activation. Furthermore, we made use of the activation-reporter property of MEM 148 to analyze the different aLp2 affinity states required for ICAM-1 and ICAM-3 binding. Unlike ICAM-1 binding, which required only one activating agent, aLp2/ICAM-3 binding required both Mg/EGTA and an activating mAb. This suggests that aLp2 with intermediate affinity is sufficient to bind ICAM-1 but not ICAM-3, which requires a high affinity state.