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CD38 Plays a Dual Role in Allergen-Induced Airway Hyperresponsiveness

¹ Integrated Department of Immunology, National Jewish Health and University of Colorado and Health Sciences Center, Denver, Colorado; ² Department of Pathology, University of Colorado Health Sciences Center, Denver, Colorado; ³ Division of Pulmonary Medicine, Department of Medicine, National Jewish Health, Denver, Colorado

Correspondence and requests for reprints should be addressed to Anne-Laure Perraud, Ph.D., Department of Immunology, National Jewish Health, 1400 Jackson St., Denver, CO 80206. E-mail: perrauda{at}njhealth.org

The multifunctional surface protein CD38 acts as a receptor with ecto-enzymatic activity, hydrolyzing NAD to generate several products known to exhibit Ca²⁺-mobilizing properties. Although CD38 is a convenient marker of immune cell development, and an indicator of progression for several diseases, it is not restricted to the immune compartment. To determine the potentially multilayered involvement of CD38 in allergen-induced airway inflammation and hyperreactivity, we dissected the potential role of CD38 as a regulator of immunity, but also pulmonary function. CD38-deficient and wild-type (WT) mice were sensitized and airway challenged with ovalbumin, and subsequently analyzed regarding their level of airway hyperresponsiveness (AHR) in response to methacholine. Parameters of lung inflammation were also analyzed. Similar sets of measurements were obtained from reciprocal bone marrow swapping experiments between CD38^–/– and WT mice. Mice lacking CD38 exhibit strongly reduced AHR, which is accompanied by a decrease in typical hallmarks of pulmonary inflammation, including eosinophilia and lymphocytic lung infiltrates, as well as Th2-cytokine levels (IL-4, -5, and -13). Antigen-specific immunoglobulin (Ig)E and IgG1 antibody titers are substantially reduced, consistent with CD38 being crucial for mounting a primary humoral systemic immune response. Reconstitution of lethally irradiated, lung-shielded, CD38-deficient mice with WT bone marrow does not restore WT levels of airway hyperreactivity, nor mucus secretion. The opposite experiment, transferring CD38^–/– bone marrow into WT mice, also shows reduced AHR levels. These studies demonstrate that CD38 not only acts as a key modulator of the immune response, but also plays an equally important role as an intrinsic pulmonary component.

Key Words: airway hyperreactivity • pulmonary inflammation • CD38 knockout mouse • bone marrow chimera

CLINICAL RELEVANCE This study demonstrates that CD38, a surface marker with NAD-hydrolysis activity generating several Ca2+-mobilizing agents, plays a dual role in a mouse model of allergen-induced airway hyperresponsiveness.