title: High dose allergen stimulation of T cells from house dust mite-allergic subjects induces expansion of IFN-gamma+ T Cells, apoptosis of CD4+IL-4+ T cells and T cell anergy.
abstract: BACKGROUND
  During clinically effective allergen-specific immunotherapy a shift in cytokine dominance from IL-4, IL-5 predominant to IFN-gamma predominant has been observed. As antigen concentration influences Th cell priming, this study aimed to determine the effect of different allergen concentrations on human house dust mite (HDM)-specific T cell production of IL-4 and IFN-gamma, proliferation and apoptosis.
  
  
  METHODS
  HDM-allergic donor PBMC were cultured for 14 days with different concentrations of HDM extract (1, 10 and 100 microg/ml). T cell intracellular IL-4 and IFN-gamma, division (CFSE labelling) and apoptosis (active caspase-3 staining) were analysed by flow cytometry. Proliferation was assessed by (3)H-thymidine incorporation.
  
  
  RESULTS
  Increased CD4+IFN-gamma+ and CD8+IFN-gamma+ T cell numbers were observed in high allergen concentration cultures compared with low concentration cultures whereas there were no differences in CD4+IL-4+ and CD8+IL-4+ T cell numbers. CFSE cell labelling revealed that high allergen concentration favours the expansion of IFN-gamma-producing CD4+ T cells. The proportion of apoptotic cells increased with allergen concentration and there was preferential apoptosis of CD4+IL-4+ T cells. HDM-induced proliferation was decreased in high allergen concentration cultures; this was reversible by IL-2 consistent with anergy.
  
  
  CONCLUSIONS
  These results show that T cell division and apoptosis contribute to the cytokine skewing to predominant IFN-gamma production by T cells observed at high allergen concentration. Thus the use of hypoallergenic T cell reactive preparations which can be given safely at higher doses than natural extracts may enhance efficacy of allergen-specific immunotherapy.
authors.affiliation: Department of Pathology and Immunology, Monash University, Alfred Hospital, Melbourne, Vic, Australia.
authors.forename: Leanne M
authors.initials: LM
authors.lastname: Gardner
authors.forename: Robyn E
authors.initials: RE
authors.lastname: O'Hehir
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Rolland
mesh_terms: D000485:Allergens / Q000276:immunology*; D039741:Antigens, Dermatophagoides / Q000276:immunology*; D017209:Apoptosis / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D017635:Clonal Anergy / Q000276:immunology; D003888:Desensitization, Immunologic / Q000379:methods*; D004306:Dose-Response Relationship, Immunologic; D005434:Flow Cytometry; D006801:Humans; D007371:Interferon-gamma / Q000097:blood* / Q000276:immunology; D015847:Interleukin-4 / Q000097:blood* / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology
chemical_list: D000485:Allergens; D039741:Antigens, Dermatophagoides; D015847:Interleukin-4; D007371:Interferon-gamma