Background: Eosinophils and their secreted mediators are heavily implicated as effector cells in asthma and other allergic diseases. Comparisons were made between expression of CD45, CD45RA, CD45RB and CD45RO by eosinophils from asthmatic patients and non-asthmatic atopic and non-atopic, non-asthmatic control subjects.
Methods: Twenty-seven patients with asthma and 33 control subjects were recruited for the study. Eosinophil expression of CD45, CD45RA, CD45RB and CD45RO was established by immunostaining and flow cytometry was performed on whole leucocyte samples. Eosinophil apoptosis in response to CD45 and CD45 isoform monoclonal antibody (mAb)-dependent receptor ligation was assessed by binding of annexin V and flow cytometry.
Results: Eosinophils from patients with asthma expressed significantly (P<0.05) higher levels of pan-CD45 and CD45RO compared with eosinophils from non-asthmatic, non-atopic subjects. No significant correlations were found between expression of either pan-CD45 or CD45RO and the degree of symptoms in the asthmatic patients as defined by lung function (FEV1 and FEF25-75) and methacholine PD20. Increased expression of pan-CD45 or CD45RO did not appear to be a consequence of the atopic phenotype. Higher expression of pan-CD45 or CD45RO by eosinophils from asthmatic patients was not associated with greater sensitivity to CD45 and CD45RO mAb receptor ligation-induced eosinophil apoptosis.
Conclusion: Higher expression of CD45 and CD45RO by eosinophils from asthmatic patients appeared to be a consequence of asthma rather than atopy and further supports a role for activated eosinophils in asthma.