The interleukin-12 family: new players in transplantation immunity?

Since several years ago, interleukin (IL)-12 is known to be responsible for the differentiation of naive CD4+ T cells into type 1 helper T cells producing interferon-gamma. Recently, two other cytokines of the IL-12 family, IL-23 and IL-27, were shown to play key roles in experimental autoimmune disorders mediated by Th17 cells, a novel pro-inflammatory CD4+ T-cell subset secreting IL-17. As our knowledge of IL-12 family members is rapidly growing and changing, it will be important to specify their involvement in the induction and regulation of allograft rejection in animal models as well as in clinical settings. Herein, we review key features of cytokines belonging to the IL-12 family and discuss their potential relevance to transplantation immunity.