History of immunology <ul><li>‘ Infectious agents’: Robert Koch, late 19 th century </li></ul><ul><li>Louis Pasteur, 1880, vaccines against cholera in chicken, rabies in humans </li></ul><ul><li>Emil von Behring and Shibasaburo Kitasano (1890’s): ‘antitoxic’ activity in serum of animals immune to diphtheria or tetanus </li></ul>
Functions of the immune system <ul><li>Protection against invaders </li></ul><ul><li>Removal of dead or damaged tissues </li></ul><ul><ul><li>RBC </li></ul></ul><ul><ul><li>Wounds </li></ul></ul><ul><li>Recognition and removal of abnormal or foreign cells or substances </li></ul><ul><ul><li>Malignancies </li></ul></ul><ul><ul><li>Transplanted tissue </li></ul></ul><ul><ul><li>Foreign bodies/substances </li></ul></ul>
Organization of the immune system External defenses Internal defenses Anatomical barriers Body secretions and excretions Normal commensal flora Cilia Innate immunity Adaptive immunity Humoral immunity Cell-mediated immunity Phagocytic cells Chemicals Complement Acute phase proteins Cytokines etc. The immune system
… Internal defenses Innate immunity Adaptive immunity Humoral immunity B cells Plasma cells Antibody Cell-mediated immunity CD4+ T cells Th1 cells Th2 cells Treg cells Th17 cells CD8+ T cells Subtypes NK T cells Phagocytic cells Neutrophils Macrophages Dendritic cells NK cells Chemicals Complement Acute phase proteins Cytokines
Innate immunity Adaptive immunity Preformed mediators- immediate effect Non-specific recognition (pattern recognition receptors) No memory, no improvement in performance during future exposure to same antigen Effectors need clonal expansion- takes days Highly specific recognition (T cell receptors and antibody) Memory: enhanced performance during future exposure to same antigen
Figure 1-11 Lymphocytes circulate between blood and lymph : Naïve lymphocytes recirculate constantly through peripheral lymphoid tissue, here illustrated as a lymph node behind a knee or popliteal lymph node. Here they may encounter their specific antigen, draining from an infected site on the foot. These so-called draining lymph nodes are sites at which lymphocytes may become activated by encountering their specific ligand.
Figure 1-12 What happens when bacteria are phagocytosed? Cytokines = chemical messengers between cells, bind to receptors on target cells, change activation, behavior and differentiation of target cells. Chemokines = type of cytokine that attracts and activates target cells
Figure 1-13 Dendritic cells form the link between the innate and adaptive immune systems.
Figure 1-14 The development of the lymphocyte receptor repertoire in the thymus and the clonal selection hypothesis .
Figure 1-16 Schematic representation of antibody structure. Fab region Fc region
Figure 1-20 Memory is an important feature of the adaptive immune response.
Figure 1-22 The most important antigen presenting cells .
The distribution of lymphocyte subpopulations in human peripheral blood. As shown on the outside of the circle, lymphocytes can be divided into T cells bearing T-cell receptors (detected with anti-CD3 antibodies), B cells bearing immunoglobulin receptors (detected with anti-immunoglobulin antibodies), and null cells including natural killer (NK) cells, that label with neither. Further divisions of the T-cell and B-cell populations are shown inside. Using anti-CD4 and anti-CD8 antibodies, a:b T cells can be subdivided into two populations, whereas : (gamma:delta) T cells are identified with antibodies against the : T-cell receptor and mainly lack CD4 and CD8.
Figure 1-25 The result of activation of a cytotoxic T cell (CD8+ T cell) by a virus infected cell:
Figure 1-26 The result of activation of a T helper cell by a macrophage infected by an intracellular pathogen like TB is that the T cell activates the macrophage, thereby enabling it to kill its invader.
Figure 1-27 Antigen presentation Antigen is recognized by T cells only if presented by antigen presenting cells on MHC molecules.