Daniela Kantárová, Milan Buc
B and T cells, respectively, provide specific immune response to antigens. While B cells are responsible for antigen immune response, T cells are major players of cell mediated immunity. On the basis of their different membrane molecules and different biological functions, T cells can be divided into three basic subsets: helper, cytotoxic, and regulatory. Within each T cell population, especially T helper cells (TH), other subsets can be identified. So, we recognize six well defined T helper cell subsets: TH1, TH2, TH17, TH5, TH9, and TH22, respectively. Each subset mediates specific physiological functions. However, when a dysregulation of immune responses happens, T cell subsets take part in immunopathological processes. The differentiation of T helper cells into particular subsets is flexible. T cells can re-differentiate into other subsets depending on the microenvironment in which the immune response proceeds. T cells need other cells to perform their activities, especially antigen presenting cells (APCs). APCs process protein antigens to forms recognizable by antigenic receptors of T cells; their HLA or CD1 molecules are necessary for this purpose.