IL-4 upregulates FcϵRI α-chain messenger RNA in eosinophils

Abstract

By using the reverse transcription polymerase chain reaction and Southern blot hybridization, we demonstrated that FcϵRI α-chain (FcϵRIα) messenger RNA was expressed in eosinophils purified from the peripheral blood of patients with allergic rhinitis and that this expression was enhanced by IL-4. However, studies in which flow cytometry or immunostaining was used did not reveal the expression of FcϵRIα protein on eosinophils from peripheral blood. Neither IL-4 alone nor the combination of IL-4 and other cytokines could induce detectable FcϵRIα protein; nevertheless, they do express FcϵRIα mRNA. Double-labeling immunostaining on cryostat sections of nasal mucosa clearly demonstrated that some FcϵRIα-positive cells were eosinophil cationic protein-positive, which confirms their eosinophilic nature. Not all the eosinophil cationic protein-positive cells express an FcϵRIα signal. Considering that FcϵRIα mRNA was detectable in four of five samples of eosinophils from those patients with nasal allergy and that only one of five eosinophil samples from normal subjects expressed FcϵRIα mRNA, the level of FcϵRI expression may be correlated with the activation of eosinophils. It seems very likely that some other unidentified factors are required for the process from the expression of FcϵRIα mRNA to that of FcϵRI as a protein. (J A LLERGY C LIN I MMUNOL 1995;96:1161-9.)