Lecture 18-1 Essentials of Immunology

Transcription

1 How does our body defend itself? Lecture 18-1 Essentials of Immunology CHAPTER 22 in BROCK BIOLOGY OF MICROORGANISMS School of Life Science and Biotechnology, Shanghai Jiao Tong University

2 Shanghai Jiao Tong University I. Overview of Immunity Immunity-the ability of an organism to resist infection non specific immunity the general ability of certain cells to resist most pathogens Cell to cell level specific immune response a highly sophisticated mechanism found in vertebrates for developing resistance to individual pathogens Cell to cell level and Proteins to cell level Shanghai Jiao Tong University

3 Shanghai Jiao Tong University 18.1 Cells and Organs of the immune system p.729 Body fluids 体液 blood and lymph Cellular blood components 1. Red blood cells-oxygen carrying 2. white blood cells-leukocytes 白细胞 phagocytic cells 吞噬细胞 Lymphocytes 淋巴细胞 3. platelets-for leakage prevention Non-cellular blood components 1. Plasma 血浆 -An important component of plasma is fibrinogen 纤维蛋白原 2. Serum 血清 -thhe fluid left after plasma clotting Shanghai Jiao Tong University

4 Shanghai Jiao Tong University Cells and Organs of the immune system Lymph 淋巴 -similar with blood but without red blood cells Lymphatic system-a separate circulatory system through which lymph circulates Lymph nodes and spleen 淋巴结与脾 -contain high concentrations of leukocytes, are the sites of most immune responses. Shanghai Jiao Tong University

5 Shanghai Jiao Tong University Cells and Organs of the immune system Phagocytes 吞噬细胞 nonspecific immunity antigen-presentation 抗原提呈 Lymphocytes 淋巴细胞 derived from the stem cells in bone marrow B lyphocytes-mature in bone marrow (or bursa in birds) T lymphocytes-mature in thymus Primary lymphoid organs-for maturation of lymphocytes thymus, bursa and bone marrow Secondary lymphoid organs-for residence of lymphocytes lymph nodes, spleen, mucosa-associated lymphoid tissue (MALT) Shanghai Jiao Tong University

6 Overall view of the lymph system, showing the locations of major organs

7 Communication between the lymph and blood system

8 Extravasations 外渗 Both blood and lymph capillaries are closed vessels, but cells and fluids can pass from one vessel to another by a process known as extravasation

9 Lymph node 淋巴结 输入管 副皮质区 皮质区 骨髓浆细胞 输出管

10 Shanghai Jiao Tong University 18.2 Non-specific immunity Phagocytes 吞噬细胞 Contact with pathogen, engulf and destroy pathogen and digest remains of pathogen to process and present antigens Motile and move by ameboid action. Most have granular inclusion called lysosomes. 1. Neutrophiles or polymorphonuclear leukocytes(pmns) 噬中性粒细胞或多形核白细胞 2. Macrophages 巨噬细胞 fixed to tissue surface antigen presenting cells 3. Monocytes-circulating precursor of macrophage 单核细胞 Shanghai Jiao Tong University

11 Shanghai Jiao Tong University Phagocytosis 噬菌作用 Anaerobic respiration lactic acid production activity of lysosomes Toxic oxygen species hydrogen peroxide superoxide anions hydroxyl radical Shanghai Jiao Tong University

12 Generation of toxic oxygen species in phagocytes

13 How can some pathogen get around phagocyte action? 1. To protect cells from toxic oxygen species Carotenoids by Staphylococcus aureus Cell wall associated glycolipids by Mycobacterium tuberculosis 2. To kill phygocytes leukocidins by Staphylococcus aureus 3. Cell surface alteration Capsule (capsulated bacteria are highly resistant to phagocytosis) M-protein (it can alter the surface of the bacterial cell and inhibits phagocytosis) Opsonization 条理作用 reversion of the protective effects of capsules by antibody

14 18.3 Specific immunity 特异性免疫 Cell-mediated immunity (CMI) and cellular immunity: antigen-receptor interaction Antigen-specific cells: T cells recognize the peptide antigen through antigenspecific T-cell receptors (TCR) located on the surface of the T cells. T-cytotoxic cells (T C cells): directly attack and destroy antigen-bearing cells T-helper cells (T H 1 cells): act indirectly by secreting proteins called cytokines that activate other cells to destroy the antigen-bearing cells. Natural killer cells: destroying foreign cells Humoral immunity: antigen-antibody interaction T H 2 cells: interact with antigen-specific B cells and stimulate the B cells to make antibodies. B cells

15 Overview of the immune response three mechanisms: (1) nonspecific immunity; (2) antibody-mediated immunity; and (3) cell-mediated immunity

16 Shanghai Jiao Tong University Basic characteristics of immunity 1. Specificity antigen-t cell antigen-antibody (produced by B cells) 2. Memory 3. Tolerance Shanghai Jiao Tong University

17 1. Specificity of immunity

18 2. Memory of immunity

19 3. Tolerance of immunity

20 II. Antigens, T Cells, and Cellular Immunity

21 Shanghai Jiao Tong University 18.4 Immunogens and antigens Immunogen 免疫原 -a molecule capable of eliciting an immune response foreign molecules, macromolecular components of the pathogen Antigen 抗原 -a molecule capable of interacting with specific components of the immune system. when recognized by the immune system, they can react with: T cell receptors antibodies Shanghai Jiao Tong University

22 Shanghai Jiao Tong University Intrinsic Features of Immunogens: Molecular size: most immunogens have a molecular weight of 10,000 or greater. Molecular complexity: nucleic acids and lipids tend to be very poor immunogens because they are composed of repeating monomers. Physical forms: complex macromolecules in insoluble form are usually excellent immunogens. Shanghai Jiao Tong University

23 Shanghai Jiao Tong University Extrinsic Features of Immunogens: The dose of the immunogens: 10μg-1g are appropriate and effective in almost any mammal. The route of administration: by injections are normally more effective than by mouth Foreign nature of the immunogen: self proteins are not recognized by the immune response. Shanghai Jiao Tong University

24 Shanghai Jiao Tong University Haptens and epitopes 半抗原与抗原决定基 Haptens 半抗原 low molecular weight substances does not induce immune response can be recognized by antibodies Antigenic determinants or Epitopes 抗原决定基 antigenic determinants distinct portion of an antigenic macromolecule recognized by individual antibodies Homologous antigen: antigen which induced the antibody Heterologous antigen: can react with the antibody that is induced by other antigen Cross reaction-reaction between antibody and a heterologous antigen Shanghai Jiao Tong University

25 Antigens and epitopes Antigens may contain several different antigenic determinants, each capable of reacting with a specific antibody.

26 Shanghai Jiao Tong University Shanghai Jiao Tong University