The profile of the cytokines secreted during the generation of T-helper cells from atopic asthmatic subjects

Systemic aspects of allergic disease: the role of the bone marrow

In recent years, there has been an increasing appreciation of the important contribution of bone-marrow-related, hemopoietic mechanisms to allergic diseases. Eosinophil/basophil-progenitor levels fluctuate in the peripheral blood during allergen exposure and the cells home to peripheral tissue, where they differentiate. It is becoming apparent that several cytokines, particularly IL-5, have multiple effects on progenitors and allergic inflammation. Within the past few years, studies of the therapeutic implications of this bone marrow contribution to atopy have been initiated; the effects of corticosteroids, leukotriene-receptor blockers, antagonism of IL-5 and modulation of differentiation by retinoic acid on progenitors will be reviewed.

IL-5 production by bone marrow stromal cells: implications for eosinophilia associated with asthma

BACKGROUND

Eosinophil infiltration of bronchial tissue is a hallmark of asthma. Recruitment of eosinophils into pulmonary tissue is dependent on the presence of IL-5. In addition, IL-5 plays a significant role in the differentiation, proliferation, and maturation of eosinophil progenitor cells in the bone marrow before recruitment into the lung. The contribution of bone marrow eosinophil production to eosinophilia associated with asthma is poorly understood.

OBJECTIVE

The aims of this study were to determine whether bone marrow stromal cells produce IL-5 and to determine whether IL-5 production by stromal cells is upregulated by IL-1, an inflammatory cytokine associated with asthma.

METHODS

IL-5 messenger (m)RNA from bone marrow stromal cells was amplified by RT-PCR and sequenced. Stromal cells were lysed, and IL-5 protein production was measured by ELISA. Upregulation of stromal cell IL-5 transcription, translation, and functional effect on eosinophil differentiation was evaluated after stimulation with recombinant IL-1alpha and IL-1beta and compared with untreated cells.

RESULTS

Bone marrow stromal cells transcribe and translate IL-5. The nucleotide sequence of IL-5 mRNA from stromal cells was identical to that previously reported for murine T cells. IL-5 mRNA abundance in stromal cells increased with increasing cell confluence in culture. IL-5 mRNA and protein levels were upregulated by exposure of stromal cells to the inflammatory cytokines IL-1alpha and IL-1beta. Exposure of stromal cells to IL-1 resulted in increased eosinophil differentiation in coculture experiments with nonadherent bone marrow cells.

CONCLUSION

The production of IL-5 mRNA and protein by bone marrow stromal cells is a novel finding that has implications for both normal eosinophilopoiesis and development of the accelerated eosinophil production associated with asthma.