Using immunohistochemistry and a panel of monoclonal antibodies, we have compared T-lymphocyte, eosinophil, macrophage, and neutrophil infiltration in bronchial biopsies from 10 intrinsic (nonallergic) asthmatics (IA) and seven extrinsic (allergic) asthmatic (EA), with similar degrees of disease severity. The results were compared with 12 normal healthy nonatopic controls (NC). All subjects were nonsmokers and were not taking oral or inhaled corticosteroids. An intense mononuclear cell infiltrate was identified in IA with an increase in the number of CD45+ cells (total leukocytes), CD3+ and CD4+ lymphocytes, and CD68+ macrophages (p < 0.03, p < 0.01, p < 0.03, and p < 0.03, respectively), compared with NC. Increases were also found in CD4+ (p < 0.05) and CD68+ (p < 0.05) cell numbers between IA and EA. IL-2 receptor-bearing cells (CD25+) and the number of total (MBP+) and actively secreting (EG2+) eosinophils, were also increased in IA compared with NC (p < 0.01, p < 0.01, and p < 0.01, respectively). Similar increases in EG2+ eosinophils and CD25+ (IL-2 receptor-positive) cells were observed in EA (p < 0.01 and p < 0.02, respectively). No differences were detected in the three groups for the number of elastase-positive cells (neutrophils). EG2+ numbers in IA correlated with the Aas asthma symptoms score (r = 0.65, p < 0.05), whereas EG2+ cell numbers in all asthmatics (IA + EA) correlated with airway methacholine responsiveness (r = -0.55, p < 0.03) and with the Aas asthma symptom score (r = 0.54, p < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)