| Summary: | Regulation of the heterogeneous cell types and mediators that constitute the immune system is achieved, in part, by the activity of CD4+ T lymphocytes. Their effector functions are induced following ligation of antigen specific receptors expressed on the cell surface of the CD4+ T cells by peptides bound to major histocompatibility complex class II proteins, in conjunction with costimulatory signals provided by antigen presenting cells. Qualitative and quantitative differences in CD4+ T cell effector functions allow the immune system to maintain homeostasis through its ability to promote productive immunity or induce tolerance. The failure of CD4+ T cells to recognise antigen or stimulate inappropriate immune responses will also influence the outcome of immunity, the resolution of inflammation and in some circumstances, therefore, may compromise the host. The research reported here investigates the biology and regulation of CD4+ T cell responses to antigens capable of inducing inflammation of the influenza virus and mycobacteria, is described. CD4+ T cells also contribute to chronic airway inflammation that occurs in susceptible individuals when they are exposed to environmental allergens and the characteristics of allergen reactive T cells are defined for responses to house dust mite derived allergens. Molecular studies complete the research on T cell antigen recognition and provide the scientific basis for the development of both <i>in vitro</i> and <i>in vivo</i> experimental models of CD4+ T cell targeted immunotherapy. The observations for this analysis has potential practical applications in the regulation of allergic inflammation. In summary, the research reported here explores the biology of CD4+ T cells specific for different antigens associated with respiratory inflammation and their potential to act as targets in the induction of protective immunity or the modulation of unwanted immune responses.
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