Application of monoclonal antibodies against major basic protein (BMK‐13) and eosinophil cationic protein (EG1 and EG2) for quantifying eosinophils in bronchial biopsies from atopic asthma

Abstract

Summary A monoclonal antibody prepared against the eosinophil major basic protein (MBP) was compared with the anti‐eosinophil cationic protein (ECP) antibodies (Eg1 and EG2) in immunostaining of bronchial biopsies from atopic asthma and controls. Anti‐MBP (designated BMK‐13) did not cross‐react with other eosinophil basic proteins (i.e. ECP, eosinophil peroxidase [EPO] or eosinophil‐derived neurotoxin [EDN]) and stained more than 98% of peripheral blood eosinophils irrespective of their degree of activation. EG2 stained 15% of resting and 75% of activated eosinophils; EG1 recognized 74% and 78% of resting and activated cells, respectively. The numbers of BMK‐13, EG1 or EG2‐positive staining cells in bronchial biopsies from asthma were significantly greater than atopic non‐asthmatics ( P < 0.02, P < 0.01 and P < 0.05, respectively) and normal non‐atopic controls ( P < 0.001). For each of the various groups studied, the rank order for the number of eosinophils stained was BMK‐13 > EG1 > EG2. BMK‐13 stained significantly more cells from bronchial biopsies of atopic asthma and atopic non asthma when compared to EG2( P < 0.001 and P < 0.05, respectively). Since only a proportion of BMK‐13 + cells were EG2 + , these results suggest that not all tissue eosinophils are actively secreting. Thus, BMK‐13 can serve as a useful pan‐eosinophil marker in tissue sections since it appears to stain most eosinophils.