Chapter 20

Transcription

1 Chapter 18 Defense Mechanisms of the Body

2 Immunology: Defenses Against Foreign Matter Immune defenses may be nonspecific, in which the identity of the target is not recognized, or it may be specific, in which it is recognized. 異 不 行 異 行

3 I. Cells Mediating Immune Defenses The cells of the immune system are leukocytes (neutrophils, eosinophils, basophils, monocytes, and lymphocytes), plasma cells, macrophages (derived form monocyte), macrophage-like cells, and mast cells. The leukocytes use the blood for transportation but function mainly in the tissues. ( 淋 ) ( 來 ) 類 利

4 Cytokines Cells of the immune system (as well as some other cells) secrete protein messengers that regulate immune responses and are collectively termed cytokines. ( ) 泌

5 II. Nonspecific Immune Defenses 異 The most common identity tags are carbohydrates or lipids that are constituents of microbial cell walls. ( ) 見 (I) Defenses at Body Surfaces External barriers to infection are the skin, the linings of the respiratory, gastrointestinal, and genitourinary tracts, the cilia of these linings, and antimicrobial chemicals in glandular secretions. 泌 尿 泌

6 (II) Inflammation (a) Vasodilation and Increased Permeability to Protein This causes net filtration of plasma into the interstitial fluid and the formation of edema.

7 (b) Chemotaxis (1) Endothelial cells in the injured area release chemoattractants and regulate the appearance of adhesion molecules on both the neutrophil and the endothelial cells. The neutrophil is loosely tethered to the endothelial cells at this stage.

8 (2) These chemoattractants act on the neutrophil to induce the appearance of another class of adhesion molecules in the neutrophil plasma membrane molecules that bind tightly to their matching molecules in the endothelial cells. (3) Via still other adhesion molecules, a narrow projection of the neutrophil is inserted into the space between two endothelial cells, and squeezes through the endothelial wall into the interstitial fluid. 兩

9 (c) Killing by Phagocytes 獵 殺 The key actors are the cells that function as phagocytes, the most important phagocyte are the neutrophils, monocytes, macrophages, and macrophage-like cells. These cells also secrete many inflammatory mediators. 類 行 類 泌

10 ( ) Opsonin enhances phagocytosis. Enzymes in the phagolysosome membrane produce nitric oxide and hydrogen peroxide, which are destructive to the microbe s macromolecules. 理

11 異 泌 路 The phagocytes release antimicrobial substances into the extracellular fluid.

12 (d) Complement ( 理 ) 行 刺 泌

13 C3b 異 Alternate complement pathway initiated as the result of interactions between carbohydrates on the surface of the microbes and inactive complement molecules. These interactions lead to formation of C3b. C3b acts as an opsonin. 路 C3b C3b 理

14 (III) Interferons (a) 數 泌 (b) 泌 (c) (d) Interferons are a family of cytokines.

15 III. Specific Immune Defenses 異 (I) Lymphoid Organs and Lymphocyte Origins 淋 淋 (a) Lymphoid Organs 淋 The lymphoid organs are categorized as primary (bone marrow and thymus) or secondary (lymph nodes, spleen, tonsils and lymphocyte collections in the linings of the body s tracts). 淋 淋 ( ) 淋 ( 淋 淋 )

16 The primary lymphoid organs are the sites of maturation of lymphocytes that will then be carried to the secondary lymphoid organs, which are the major sites of lymphocyte cell division and specific immune responses. 淋 淋 行 淋 淋 淋 行 裂 異 Lymphocytes undergo a continuous recirculation among the secondary lymphoid organs, lymph, blood, and all the body s organs and tissues. (polymorphonuclear granulocytes and monocytes do not recurculate) 淋 淋 淋 不 行 ( 粒 不 )

17 (b) Lymphocyte Origins 淋 淋 T T

18 (II) Functions of B Cells and T Cells B T 識 殺 cytototoxic T cell CD8+ cell T CD8 Helper T cell CD4+ cell T CD4

19 (III) Lymphocyte Receptors 淋 (a) B-Cell Receptors B B-cell surface plasma-membrane receptors are copies of the specific antibody (immunoglobulin). Any given B cell or clone of B cells produces antibodies that have a unique antigen-binding site. B cells possess the enzymes required to catalyze the process of DNA rearrangememts. B ( ) B B B DNA

20 ( ) 異

21 (b) T-Cell Receptors T T-cell surface plasma-membrane receptors are not immunoglobulins, but they do have specific antigen binding sites that differ from one T-cell clone to another. DNA rearrangements occur during T-cell maturation. T 不 不 T 不 T DNA The T-cell receptor binds antigen only when the antigen is complexed to one of the body s own plasma-membrane MHC proteins. MHC T

22 Class I MHC proteins are found on all nucleated cells of the body, whereas class II MHC proteins are found only on macrophages, B cells, and macrophagelike cells. Cytotoxic T cells (CD8 protein) require antigen to be bound to class I proteins, whereas helper T cells (CD4 protein) require class II proteins. MHC MHC B 類 T (CD8 ) 識 MHC T (CD4 ) 識 MHC

23 (IV) Antigen Presentation to T Cells T (a) Presentation to Helper T Cells T (A) (B)B 理 T 類 MHC

24 1 (APC) MHC T 2 T 刺 3 泌 1 T (APC)

25 (b) Presentation to Cytotoxic T Cells T 糖 類 MHC Viral proteins are endogenous antigen, foreign protein synthesized by a body cell. Full activation of cytotoxic T cells requires costimulus. 來 T 刺

26 (V) NK Cells 殺 NK cells have the same targets as cytotoxic T cells, but they are not antigenspecific. MHC proteins are not involved in the activation of NK cells. 殺 T 不 異 MHC 殺

27 (VI) Antibody-Mediated Immune Responses: Defenses against Bacteria, Extracellular Viruses, and Toxins IL-1 and TNF stimulate the helper T cell to secret IL-2 and to express the receptor of IL-2. This messenger acts as an autocrine agent. 1 刺 T 泌 泌

28 (a) Antibody Secretion 泌 There are five major classes of secreted antibodies: IgG, IgM, IgA, IgD, and IgE. IgG and IgM are the major antibodies against bacterial and viral infection. IgE participate in defenses against multicellular parasites and allergic responses. IgA act locally in the linings or secreted in milk. IgG, IgM, IgA, IgD IgE IgG IgM IgE IgA

29 (b) The Attack: Effects of Antibodies Direct Enhancement of Phagocytosis Fc

30 (c) Activation of the Complement System

31 (d) Antibody-Dependent Cellular Cytotoxicity (ADDC) NK cells can bind nonspecifically to the Fc portion of antibodies bound to antigen. 殺 Fc 異 (e) Direct Neutralization of Bacterial Toxins and Viruses

32 (VIII) Defenses against Virus-Infected Cells and Cancer Cells (a) Role of Cytotoxic T Cells T 洞

33 (b)role of NK Cells and Activated Macrophages 殺 (1) Non specific cell-killing 異 殺 Helper T cells activation is a specific immune response. T 2 (2) Antibody-dependent cellular cytotoxicity (ADDC)