Editorial: Understanding Gamma Delta T Cell Multifunctionality - Towards Immunotherapeutic Applications.

Introduction: gd T cells have been characterized by the expression of a gd T cell receptor (TCR).When the gd TCR and the corresponding ab TCR were first discovered it was assumed that the corresponding cell types were likely to be functionally very similar. However, some 30 years later, we have realized that they are not. Unlike ab T cells, gd T cells (i) sense target antigens independent of MHC molecules; (ii) display NK-cell like innate reactivities, including killing of infected cells as well as microbes; (iii) are able to take up large particulates, including bacteria, and (iv) can act as professional antigen presenting cells. The “stress sensing” abilities of gd T cells have led to a great interest in exploring their potential use in novel immunotherapies, not least in cancer. In addition, their capacity to produce various cytokines and to interact with other cells, such as lymphocytes, myeloid cells, and neutrophils, has raised an interest in their potential therapeutic use as immunomodulators. gd T cells have therefore recently come to stand out as a distinctly unique cell type. At the same time, we have come to realize that gd T cells are likely to be an ancient cell type with ancestors as far back as in our common ancestors to jawless fish and thereby, potentially predating the development of our adaptive immune system. It is clear that to make full use of the great potential of gd T cells in immunotherapeutic interventions, we must significantly improve our understanding of the extensive plasticity and multifunctionality of gd T cells and of how these cells can be harnessed therapeutically, both safely and effectively. This Research Topic, contains 26 articles which includes Review, Original Research, and Methods articles in the area of gd T cell plasticity and multifunctionality, As shortly overviewed in this editorial, these articles shall not represent entire field of gd T cell biology but primarily focuses on how an increased knowledge in this area can be used and developed further toward improved immunotherapeutic applications in cancer, infectious disease, autoimmunity, and other immunity-related areas.