Interleukin produced characteristically by TH1 (A)Interleukin 2 (B)IL 5 (C)IL γ (D)INF γ (E)IL 10

The following interleukin is characteristically produced in a TH1 response - Explanation: Ans. is ‘a’ i.e., IL-2 [Ref: Robbins 7th/e p. A. T helper - 1 {TH 1) secretes → IL-2 and interferon - γ B. T helper - 2 (T[f 2) secretes → IL-4,IL-5, IL-6, EL-13 T-cells o 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. Helper/Inducer T cells These cells have CD4 surface marker and are MHC class II restricted. These are further subdivided into: - A. Effector CD4 helper T cells o These cells secrete cytokines and other products that perform all major functions, o These cells are of following types. i. TH, cells These cells are activated by IFN-γ These 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; and ii. Activating NK cells. ii. TH, cells These 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 mast Cells and eosinophils → Therefore, provide defence against Helminthic parasites. iii. TH17 cells A third subset of CD4 T-cells (besides TH1 and TH2) has been discovered recently and is Called the TH17 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 17 cells. TH17 cells are powerful recruiters of neutrophils and monocytes, and thus play major roles in severe inflammatoiy diseases. They may also be important for defense against some bacterial and fungal infections in which neutrophilic inflammation is a prominent feature. TH 17 cells are activated by some microbial antigens and by self antigens in autoimmune diseases. Activated TH17 cells secret IL-17, IL-22 and chemokines. Collectively, these cytokines recruit neutrophils and monocytes. TH17 cells produce IL-21, which amplifies the TH17 (self) response. B. Memory CD4 helper T cells o Provide memory, i.e., retain the antigenic affinity of the originally activated T cells and are used to act aslater effector cells during a second immune response. 2. Cytolytk/cytotoik T cells These 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 in Type II Hypersensitivity. 3. Suppressor T-cells These 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.