Cell-Mediated Immunity: Activation and Effector Mechanisms PDF

Cell-Mediated Immunity: Activation and Effector Mechanisms Dr. Hossein Asgarian-Omran Ph.D., Prof. of Immunology Dep. of Immunology, School of Medicine Mazandaran University of Medical Sciences...

Cell-Mediated Immunity: Activation and Effector Mechanisms Dr. Hossein Asgarian-Omran Ph.D., Prof. of Immunology Dep. of Immunology, School of Medicine Mazandaran University of Medical Sciences [email protected] Activation of T lymphocyte and recognition of antigen is done by dendritic cells in most cases  B-cell Epitopes ▪ They are peptide structure, polysaccharide, nucleic acid,… ▪They are identified directly without antigen-presenting cells ▪There are two types: linear and conformational  T-cell Epitopes Has a peptide structure Recognized with the help of antigen- presenting cells Only linear Sequence of events in T cell responses Migration of T lymphocytes to lymph nodes Antigen recognition by T lymphocytes Activation of T lymphocytes in lymphatic tissues and their executive response Clonal expansion of specific T lymphocytes Activation of T lymphocytes (the role of co- stimulatory molecules and interleukin 2) The role of interleukin 2 in the activation of T lymphocytes  Main source of production: activated T cells  Stimulator of survival, proliferation and differentiation of activated T lymphocytes  Survival and proliferation of other cells such as NK and B lymphocytes  Promoting the survival and function of regulatory T cells Different messages of antigen presenting cells to T lymphocytes The role of CTLA-4 in inhibiting the activation of T lymphocytes Therapeutic use of CTLA-4 inhibition Different subtypes of T lymphocytes Differentiation of helper T lymphocytes into different subtypes and their characteristics Effector Mechanisms of Cellular Immunity Role of T cells in eradicating infections Executive actions of Th1 helper T lymphocytes Activation of macrophages by TH1 cells Granuloma formation in some diseases due to Imperfect functioning of cellular immunity Executive functions of Th2 helper T lymphocytes Activation of macrophages from classical and alternative pathways Executive functions of Th17 helper T lymphocytes Stimulation and executive activities of killer T lymphocytes The mechanism of killing target cells by killer T lymphocytes  Release of granules  Induction of apoptosis Ingredients in granules  Perforin  Granzyme  Geranulysin Contact between killer T cell and target cell Apoptosis induction by killer T lymphocytes Mechanism of killing target cells by killer T lymphocytes  Summary Activation of T lymphocyte and recognition of antigen The role of interleukin 2 in the activation of T lymphocytes The role of CTLA-4 Different subtypes of T lymphocytes Effector Mechanisms of T helper cells Effector Mechanisms of cytotoxic T cells Figure 9-9 Structure of IL-2 and its receptor. The crystal structure of IL-2 and its trimeric receptor shows how the cytokine interacts with the three chains of to the receptor. (Reproduced from Wang X, M Rickert, and KC Garcia. Structure of the quaternary complex of interleukin-2 with its α, β and γc receptors. Science 310:1159-1163, 2005, with the permission of the publishers. Courtesy of Drs. Patrick Lupardus and K. Christopher Garcia, Stanford University School of Medicine, Palo Alto, California.) Dow nloaded from: Stude ntCons ult (on 30 Septem be r 201 1 0 6:36 PM) © 200 5 Elsevier  Figure 9-10 Regulation of IL-2 receptor expression. Resting (naive) T lymphocytes express the IL-2Rβγ complex, which has a moderate affinity for IL-2. Activation of the T cells by antigen, costimulators, and IL-2 itself leads to expression of the IL-2Rα chain and high levels of the high-affinity IL- 2Rαβγ complex. Dow nloaded from: Stude ntCons ult (on 30 Septem be r 201 1 0 6:36 PM) © 200 5 Elsevier Figure 9-11 Biologic actions of IL-2. IL-2 stimulates the survival and proliferation of T lymphocytes, acting as an autocrine growth factor. IL-2 also maintains functional regulatory T cells and thus controls immune responses (e.g., against self antigens). Dow nloaded from: Stude ntCons ult (on 30 Septem be r 201 1 0 6:36 PM) © 200 5 Elsevier Figure 9-19 Development of memory T cells. In response to antigen and costimulation, naive T cells differentiate into effector and memory cells. Some of the phenotypic markers of these cell populations are shown in A. A, According to the linear model of memory T cell differentiation, most effector cells die and some survivors develop into the memory population. B, According to the branched differentiation model, effector and memory cells are alternative fates of activated T cells. Dow nloaded from: Stude ntCons ult (on 30 Septem be r 201 1 0 6:36 PM) © 200 5 Elsevier