The present invention relates to methods for modulating the migratory activity of cells expressing CD38 for the treatment of disorders including, but not limited to, inflammation, ischemia, asthma, autoimmune disease, diabetes, arthritis, allergies, infection with pathogenic organisms, such as parasites, and transplant rejection. Such cells include, for example, neutrophils, lymphocytes, eosinophils, macrophages and dentritic cells. The invention further relates to drug screening assays designed to identify compounds that modulate the ADP-ribosyl cyclase activity of CD38 and the use of such compounds in the treatment of disorders involving CD38 modulated cell migration. Additionally, the invention relates to the isolation and characterization of a CD38 homologue from the parasitic flatworm, Schistosoma mansoni.