Anti-IL-5 attenuates activation and surface density of β(2) -integrins on circulating eosinophils after segmental antigen challenge.
Clin Exp Allergy 2013;
43:292-303. [PMID:
23414537 DOI:
10.1111/j.1365-2222.2012.04065.x]
[Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 06/14/2012] [Accepted: 06/25/2012] [Indexed: 12/12/2022]
Abstract
BACKGROUND
IL-5 activates α(M) β(2) integrin on blood eosinophils in vitro. Eosinophils in bronchoalveolar lavage (BAL) following segmental antigen challenge have activated β(2) -integrins.
OBJECTIVE
To identify roles for IL-5 in regulating human eosinophil integrins in vivo.
METHODS
Blood and BAL eosinophils were analysed by flow cytometry in ten subjects with allergic asthma who underwent a segmental antigen challenge protocol before and after anti-IL-5 administration.
RESULTS
Blood eosinophil reactivity with monoclonal antibody (mAb) KIM-127, which recognizes partially activated β(2) -integrins, was decreased after anti-IL-5. Before anti-IL-5, surface densities of blood eosinophil β(2) , α(M) and α(L) integrin subunits increased modestly post challenge. After anti-IL-5, such increases did not occur. Before or after anti-IL-5, surface densities of β(2) , α(M) , α(L) and α(D) and reactivity with KIM-127 and mAb CBRM1/5, which recognizes high-activity α(M) β(2) , were similarly high on BAL eosinophils 48 h post-challenge. Density and activation state of β(1) -integrins on blood and BAL eosinophils were not impacted by anti-IL-5, even though anti-IL-5 ablated a modest post-challenge increase on blood or BAL eosinophils of P-selectin glycoprotein ligand-1 (PSGL-1), a receptor for P-selectin that causes activation of β(1) -integrins. Forward scatter of blood eosinophils post-challenge was less heterogeneous and on the average decreased after anti-IL-5; however, anti-IL-5 had no effect on the decreased forward scatter of eosinophils in post-challenge BAL compared with eosinophils in blood. Blood eosinophil KIM-127 reactivity at the time of challenge correlated with the percentage of eosinophils in BAL post-challenge.
CONCLUSION AND CLINICAL RELEVANCE
IL-5 supports a heterogeneous population of circulating eosinophils with partially activated β(2) -integrins and is responsible for up-regulation of β(2) -integrins and PSGL-1 on circulating eosinophils following segmental antigen challenge but has minimal effects on properties of eosinophils in BAL. Dampening of β(2) -integrin function of eosinophils in transit to inflamed airway may contribute to the decrease in lung inflammation caused by anti-IL-5.
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