Syk deficiency in nonreleaser basophils

Background: Peripheral blood basophils from 10% to 20% of donors fail to de granulate in response to cross-linking the high-affinity IgE receptor Fc ep silon RI, The molecular mechanisms underlying the nonreleaser phenotype hav e not been established, Objectives: Our aim was to compare the expression of Fc epsilon RI-associat ed protein tyrosine kinases between nonreleaser and releaser basophils, Methods: With use of Western blotting we investigated Syk and Lyn protein l evels in highly purified basophils from 3 anti-IgE nonreleasers and 2 relea sers, Results: We identified 3 healthy nonatopic donors whose nonreleaser basophi ls express Fc epsilon RI normally but fail to express protein for the tyros ine kinase Syk, which is implicated in the initiation of Fc epsilon RI-medi ated secretion. Protein levels for the tyrosine kinase Lyn are somewhat red uced but not absent in nonreleaser basophils, Levels of Lyn and Syk protein are similar in B cells,eosinophils, and neutrophils from releaser and nonr eleaser donors. During these studies one nonreleaser "converted" into a rel easer with concomitant basophil Syk expression. Conclusion: The absence of detectable Syk could explain the nonreleaser phe notype of basophils from some donors.