Innate and Adaptive Immunity

2. Innate and Adaptive Immunity • Innate immunity leads to diverse responses to a pathogen • the innate immune system consists of cells and proteins that are always present and ready to mobilize and fight microbes at the site of infection • the main components of the innate immune system are 1)physical epithelial barriers, 2)phagocytic leukocytes, 3)dendritic cells, 4)a special type of lymphocyte called a natural killer (NK) cell, and 5) circulating plasma protein • Adaptive immunity helps defends against viruses. • Antigens are molecules that provoke a specific immune response and are a large part of adaptive immunity. • Characterized by specificity of recognition of antigen, wide diversity of antigens can be specifically recognized, memory, where by the immune system respond more quickly and more intensely to an antigen it encountered previously than to one it is meeting for the first time, and the ability to distinguish self-antigens from nonself • The adaptive immune system can be active or passive

3. Cells of the Immune System Helper T cell: recognizes foreign peptides on antigen-presenting cells, inducing the release of cytokines that activate b cells or macrophages Cytotoxic T cell: recognizes and kills "altered self" cells: virally infected, or tumor cells B cell: binds specific soluble antigens with its membrane-bound antibody; serves as an antigen-presenting cell to Th cells; on activation differentials into plasma and memory B cells Plasma cell: derived from activated B cells; is a biochemical factory devoted t0 the secretion of antibodies directed against specific antigens Natural killer cell: Rapidly recognizes and kills virally infected cells or tumor cells Monocyte: precursor of macrophage; located in blood system Macrophage: phagocytic tissue cell that is a component of the body's first cellular line of defence; found in large numbers in the blood until attracted to tissues during inflammation Eosinophil: Important to the elimination of parasites and involved in chronic inflammatory diseases Basophil: Circulating cell that releases mediators such as histamine that promote inflammation Mast cell: located primarily under mucosal surfaces and releases mediators such as histamine that promote inflammation; triggered both during inflammatory and allergic reactions Dendritic cell: important antigen-presenting cell naive Th cells; also helps in the activation of naive Tc cells

4. Cell-Mediated Immunity • T cells may be characterized as either cytotoxic T cells or helper T cells • cytotoxic T cells eliminate virally infected cells and tumor cells • Cytotoxic T cells destroy cells in a fashion similar to NK cells; it secretes perforin monomers that creates pores in the target's membrane, then granzymes enter and activate caspases which cause the apoptosis (destruction) of the target

5. Humoral Immunity • B cells are activated by membrane Ig molecules binding to a specific epitope on an antigen • Immunoglobulins consist of two light chain and two longer heavy-chain polypeptides • Antibodies can agglutinate, precipitate, or neutralize antigens • The five classes of immunoglobulins that determine function: IgA, IgD, IgE, IgG, & IgM • The secondary response to an antigen is more effective than the primary response • A rapid secondary response is launched due to memory cells • Flu shots/vaccination (presents the body with an antigen to elicit the primary response, then when encountered again, a pathogen is eliminated quickly by the secondary response

6. Antibody Production • Each plasma B cell is a miniature factory producing soluble antibodies of the same specificity as the membrane-bound antibodies of the parent B cell • The variable regions of the heavy and light chains fold together to form a cleft, the antigen binding site • The five classes of antibodies are based on the sequence and structure of the constant regions of their heavy chains

7. True and False • Adaptive immunity provokes a specific immune response and is large part of the innate immunity False • Cytotoxic T cells recognize foreign peptides on antigen-presenting cells, inducing the release of cytokines that activate b cells or macrophages False • T cells may be characterized as either cytotoxic T cells or helper T cells True • A primary response is more effective than the secondary response False • The variable regions of the heavy and light chains fold together to form a cleft, the antigen binding site True

8. Multiple Choice • The five classes of immunoglobulins are: A: IgA, IgD, IgE, IgG, IgM B: IgA, IgC, IgD, IgE, IgF C: IgA, IgD, IgE, IgG, IgH D: IgB, IgD, IgE, IgG, IgF Answer: A

11. Here is a video explaining how the immune system works!