The role of macrophage- and dendritic cell-derived IL12 in Th1 phenotype development

The class of immune response elicited to antigen determines whether an infectious organism is eradicated with minimum immunopathology or results in chronic disease, and is determined by the cytokine profile of the responding CD4 super(+) T cells. Furthermore, pathology accompanying inappropriate immune responses to autoantigens has been associated with production of inflammatory mediators by CD4 super(+) T cells. A number of factors, including the antigen-presenting cell, the dose of antigen, and the route of immunization have been suggested to play a role in the development of Th1 or Th2 type cells, which are responsible for such differential immune responses. However, it is now clear that cytokines are the major players in the development of CD4 super(+) T-cell subsets producing discrete cytokine profiles. Although a number of cytokines have been shown to play a role in this process, IL12 and IL4 have been shown to be dominant factors in driving Th1 and Th2 phenotype development, respectively.