A. Dakhama

Protective effects of a bacterial stimulus on IL-4 receptor expressing cells in allergen-exposed mice

A, G. Alvarez. A. Joetham, C. Taube, A. Balhorn, A. Dakhama, E. W. Gelfand; Pediatrics. National Jewish Medical and Research Center, Denver, CO. RATIONALE: IL-4 and IL-4 receptor (IL-4R) expressing cells are presumed to be effectors of allergic responses. However, the type of responses developed may be dictated by the stimulus. For these reasons, we compared the consequences of allergen/alum stimulation versus bacterial (mycobacterial) stimulation. METHODS: BALB/c mice received two i.p. injections of ovalbumin (OVA)-alum on days 0 and 14 and two intranasal challenges with OVA on days 29 and 30. A second group received a single injection of OVA-Complete Freund Adjuvant (CFA) on day 0 and two intranasal challenges with OVA on days 29 and 30. 24 h later, lung cells were isolated by collagenase digestion and further enriched for phagocytic cells by density gradient centrifugation and enriched for dendritic cells by negative selection using magnetic beads. IL-4R+ cells were stained for intracellular cytokines. RESULTS: OVA-alum sensitized and challenged mice developed airway hyperresponsiveness (AHR). Lung IL-4R+ cells showed an IFN 7. IL-10 ratio of 1:2, but IL-4 stimulation failed to trigger in vitro production of ILl0 and IL-12. Further, IL-4 failed to trigger IL-4 production in GATA-3+ cells. In contrast, mice sensitized with CFA did not develop AHR, IL-4R+ lung cells showed an IFN 7. IL10 ratio of 2:1, and addition of IL-4 in vitro induced IL-10 and IL-12 production. GATA-3+ cells from these mice stimulated with IL-4 induced the production of IL-4. CONCLUSIONS: These results indicate the importance of the stimulus in shaping the response of IL-4R+ dendritic cells and provide a potential explanation for the protective effects of bacterial stimuli on allergic responses. Funding: NIH grants HL-36577, HL-61005 and EPA grant R825702