Immune response after photodynamic therapy increases anti-cancer and anti-bacterial effects

Table 3 Common features of T regulatory cells

Features of Treg	Ref.
Phenotypic and functional specialization	[66-68]
Treg are CD4+CD25+FoxP3+ immunosuppressive T cells. They are important for the maintenance of the immune homeostasis and involved in both autoimmune disease and cancer	[71,72]
Cells subpopulations
Treg are generally classified into nTreg and iTreg. The former are found in the thymus and thought to have T-cell receptors that recognizes self-antigens, therefore important in the prevention of autoimmune disease, the latter can be induced and differentiate in the periphery, i.e., upon influence by TGF-β in the tumor microenvironment	[69,70]
Immunosuppressive mechanisms
Treg are thought to mediate their immunosuppressive effects by multiple mechanisms, among which
Secretion of immunosuppressive cytokines
High affinity binding of his CTLA-4 receptor to B7-1 and B7-2 costimulatory molecules on antigen presenting cells and transmission of inhibitory signals
Role of Treg in anti-tumor immunity	[71,73-75]
Treg are known to inhibit the generation of immune responses against tumors. Treg depletion in vivo facilitates tumor eradication and enhances-anti-tumor immunity

nTreg: Natural Treg; iTreg: Induced Treg; CTLA-4: Cytotoxic T-lymphocyte antigen 4; Treg: T regulatory cells; TGF: Transforming growth factor.