Objective:To investigate the expression and regulation of the platelet-activating factor receptor(PAF-R)in human keratinocytes.Methods:The expression of PAF-R in skin tissues and HaCaT cells was examined by immunohis-tochemistry.The expression of PAF-R in HaCaT cell mRNA level was detected by RT-PCR.The expression and regulation of PAF-R were measured by flow cytometry in HaCaT cells treated with various stimuli.Results:The expression level of PAF- R was very high in human keratinocytes,mainly located on cell membranes and cytoplasma.PAF-R also expressed on HaCaT cells transcription levels,and the tissue-type PAF-R mRNA was more than that of leucocyte-type PAF-R mRNA.PAF-R ex-pressed on both membrane and intracellar part of HaCaT cell,and the intracellular expression was about4.82times that of membrane expression.IFN-?and retinoic acid upregulated the membrane expression of PAF-R in HaCaT cell.Conclusion:Human keratinocytes can highly express PAF-R at cell,protein and transcription levels,and the expression characteristic can be regulated by some inflammatory factors,which indicates the PAF system may play an important role in the skin inflamma-tion. [