The pro-inflammatory cytokine granulocyte macrophage-colony stimulating factor (GM-CSF), secreted by AMs, promotes myeloid cell differentiation, stimulates antigen presenting cells, prolongs eosinophil survival [37] and is elevated in BAL and bronchial biopsies in asthma and after allergen challenge [38-41]. The gene discussed is CSF2; the disease is asthma.