¶ … autocrine regulation by IL-21 in the generation of inflammatory T cells" from Nature 2007 Biological background and research findings/data

This article touches upon several important and popular areas of research interest in immunology and microbiology over the past two decades. The study of CDK4+ T cells has clearly been a well-financed and prioritized research subject since the role of this type of cell was identified as essential in the pathophysiology of HIV / AIDS. IL-21 in particular was identified as a regulator in NK cell activity and terminal differentiation shortly before the start of the last century (Biron 1999). IL-21 is a cytokine, measuring 15 kDa and consisting of four alpha helixes. Prior to this paper, published as a letter in Nature in 2007, there had been three major functions of IL-21, which is secreted from activated CD4+ T cells, in immunological pathways (Neely 1997).

IL-21 was first studied as a regulator in adaptive immune response, when natural killer (NK) cells have been activated by one of many known cytokines, including IL-15, to which IL-21 is genomically similar. IL-21 has been thought to interact...

It has also been studied in the macrophage apoptotic IFN-gamma pathway. A third domain of IL-21 study has been in relation to its role in inducing apoptosis in terminally-differentiated NK cells, a stage of cell death signaling the transition from the innate immunological response to the adaptive immune response (Medzhitov 1997).
This article looked at an autocrine regulation role that IL-21 was found to have in the generation of inflammatory T cells. It was shown that the pathway of IL-21 in this pathway is STAT3 interacting with IL-6, which then induces IL-21 in T cells. It was demonstrated to be necessary for TH17 generation when STAT3 upregulated ROR-c. The autocrine function in which IL-21 has been found to operate was compared with the role of IFN-c in TH1 generation in IL-4 in TH2 generation. The authors concluded then that T cell differentiation is mediated by constituent parts of the innate immune response in a T-cell intrinsic manner via autocrine pathways, and that this represents a novel understanding of…