Upregulation of IL-5 receptor expression on bone marrow-derived CD34+ cells from patients with asthma.

BACKGROUND: Interleukin-5 (IL-5) is a potent eosinophilopoietic factor implicated in the chronic inflammatory cell accumulation accompanying bronchial asthma. We studied the expression of the IL-5 receptor alpha-subunit (IL-5R alpha) on bone marrow-derived cluster of differentiation molecule 34 positive (CD34+) progenitor cells in asthmatics to prove the ability of progenitor cells to respond to IL-5 more readily. METHODS: Non-adherent non-T cells (NANT) were separated from heparinized bone marrow blood from 6 asthmatics and 3 normal subjects, loaded with CD34+ and IL-5R alpha monoclonal antibodies conjugated with immunofluorescence and then analyzed by flow cytometry. Colonies grown from progenitor cells cultured in methylcellulose were determined for 14 days in the presence or absence of growth factors, including granulocyte-monocyte colony stimulating factor, stem cell factor, and interleukin-3. RESULTS: The proportion of IL-5R alpha expression on the CD34+ cell surface was significantly increased in asthmatics (12.9 +/- 3.3%, n = 6, p = 0.0163) compared to normal subjects (1.8 +/- 0.6%, n = 3). A significantly greater number of colonies committed to eosinophilic differentiation were found in the asthmatic subjects. CONCLUSION: We demonstrated an increased expression of IL-5R alpha on bone marrow-derived progenitor cells in asthmatics. This supports the concept that bone marrow-derived progenitor cells are ready for eosinophilopoiesis.