<prompt> Interleukin produced characteristically by TH1 AInterleukin 2BIL 5CIL γDINF γEIL 10ADBDCADE  <response>: The following interleukin is characteristically produced in a TH1 response -Explanation:Ans. is a i.e., IL-2 Ref: Robbins 7the p.A. T helper - 1 TH1 secretes IL-2 and interferon - γB. T helper - 2 Tf2 secretes IL-4,IL-5, IL-6, EL-13T-cellso T cells are amongst the two important cells of adaptive immune system others are B-cells.o T cell precursors arise in bone marrow also in yolk sac liver before birth and migrate to the thymus,o Maturity ofT-cells takes place in the thymus So, T cells arise in bone marrow and mature in thymus,o T-cells constitutes 60-70 of the circulating peripheral lymphocytes.o Based on their surface markers. target cells and functions the following T cell category have been identified:1. HelperInducer T cellsThese cells have CD4 surface marker and are MHC class II restricted.These are further subdivided into: -A. Effector CD4 helper T cellso These cells secrete cytokines and other products that perform all major functions,o These cells are of following types.i. TH, cellsThese cells are activated by IFN-γThese cells produce IL-2, IFNyand IL-12.These cells facilitate delayed hypersensitivity, cell mediated immunity. Macrophage activation,Killing of intracellular microbes e.g., tuberculosis leprosy.These cells also induce destruction of target cell by : -i. Activating CD8 T cells to become cytotoxic cells; andii. Activating NK cells.ii. TH, cellsThese cells are activated by IL-4.These cells secrete IL-4,1L-5, IL-6 and IL-13.these cells facilitates the synthesis of antibodies particularly IgE and cause activation of mastCells and eosinophils Therefore, provide defence against Helminthic parasites.iii. TH17 cellsA third subset of CD4 T-cells besides TH1 and TH2 has been discovered recently and isCalled theTH17 cells.If the antigen producing cells produce inflammatory cytokines such as IL-1, IL-6 and IL-23,These work in collaboration with TGF-3 to stimulate differentiation of T-cells to the TH 17cells.TH17 cells are powerful recruiters of neutrophils and monocytes, and thus play major roles insevere inflammatoiy diseases.They may also be important for defense against some bacterial and fungal infections in whichneutrophilic inflammation is a prominent feature.TH 17 cells are activated by some microbial antigens and by self antigens in autoimmunediseases. Activated TH17 cells secret IL-17, IL-22 and chemokines. Collectively, thesecytokines recruit neutrophils and monocytes.TH17 cells produce IL-21, which amplifies the TH17 self response.B. Memory CD4 helper T cellso Provide memory, i.e., retain the antigenic affinity of the originally activated T cells and are used toact aslater effector cells during a second immune response.2. Cytolytkcytotoik T cellsThese cells have CD8 surface marker and are MHC class I restricted.They kill and lyse target cells including tumor cells, virus infected cells and allograft; and participate inType II Hypersensitivity.3. Suppressor T-cellsThese cells have CDg surface marker and are MHC class I restricted.These cells down regulate immune response.o Helper T cell CD4 T cell is known as the master regulator of the immune system.o The ratio of CD4 and CD8 T cell is normally 2 :1. 