The complexity of the blood cell populations has grown in parallel with the development of always more sophisticated technology. From the discovery of red blood cells in 1658 by the Dutch naturalist, Jan Swammerdam, almost 200 years passed until the identification of leucocytes (1843) by two independent physicians from England and France establishing the beginning of haematology as a new field in medicine. The molecular characterization of the leucocytes required the advent of flow cytometry (1960) and monoclonal antibodies (1975). The latter were a crucial tool for the discrimination of CD4+ and CD8+ T helper cells. In the next decades the scenario of CD4+ T helper cells became more and more complicated with the discovery of distinct subclasses. In 1986 Mosman and Coffman revealed the existence of two functional subsets, termed T helper 1 (Th1) and T helper 2 (Th2). In 1995 Dr Sakaguchi, discovered another specific subpopulation of T cells, named regulatory T (Treg) cells, that were specialized for immunosuppression. More recently other subsets have been isolated named Th17 (2005),, Th9 (2008), and Th22 (2009). Finally, single‐cell RNA‐sequencing has revealed the existence of a subpopulation of steroid‐producing cells within the Th2 compartment.
Immunology. 2016 February;147(2):133-140.