Thelper cell type 1 (Thl) and 2 (Th2) play central roles in immune regulation.To identify thenovel genes differentially expressed between Th 1 and Th2 cells,CD4~+ T cells were isolated from DO 11.10transgenic mice and induced under Thl or Th2 conditions.Microarray showed differential expression ofneutrophilic granule proteins (NGP) between Thl and Th2 cells.NGP was first identified as a myeloid-specific granule protein with homology to the cystatin superfamily.Here we confirmed greater expressionof NGP in Th2 cells by reverse transcription-polymerase chain reaction and real-time polymerase chainreaction analysis.We also showed that the expression of NGP mRNA had a peak expression after 5 d cultureunder Th2- but not Thl-biasing conditions. Antibody against NGP was prepared,and in concert with theresults of mRNA analysis,the level of NGP protein in Th2 cells detected by Western blot analysis was alsohigher than that in Th1 cells.GFP-NGP fusion proteins overexpressed in HeLa cells were localized to thecytoplasm.These results suggest NGP is a novel marker distinguishing Th2 from Th1 cells and maybe anovel cytokine secreted by Th2 cells. Thelper cell type 1 (Thl) and 2 (Th2) play central roles in immune regulation. To identify then novel genes differentially expressed between Th 1 and Th2 cells, CD4 ~ + T cells were isolated from DO 11.10 transgenic mice and induced under Thl or Th2 conditions. Microarray been differential expression ofneutrophilic granule proteins (NGP) between Thl and Th2 cells. NGP was first identified as a myeloid-specific granule protein with homology to the cystatin superfamily. HEre we confirmed greater expression of NGP in Th2 cells by reverse transcription-polymerase chain reaction and real-time polymerase chain reaction assay. We also showed that the expression of NGP mRNA had a peak expression after 5 d culture under Th2- but not Thl-biasing conditions. Antibodies against NGP was prepared, and in concert with the results of mRNA analysis , the level of NGP protein in Th2 cells detected by Western blot analysis was alsohigher than that in Th1 cells. GFP-NGP fusion proteins overexpressed in HeLa cells were lo calized to the cytoplasm.These results suggest NGP is a novel marker distinguishing Th2 from Th1 cells and maybe anovel cytokine secreted by Th2 cells.