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1、2011/04/01,2,Q&A,Why doesnt the adaptive immune system normally attack your own body tissues?,2011/04/01,3,Specific Defenses of the Host： The Immune Response,Innate immunity (nonspecific)：Defenses againstany pathogen. Adaptive immunity (specific)：Induced resistanceto a specific pathogen. Immunity：Sp
2、ecific antibody and lymphocyteresponse to an antigen. Antigen (Ag) A substances that causes thebody to produce specificantibodies or sensitized T cells. Antibody (Ab) Proteins made in responseto an antigen.,2011/04/01,4,Types of Acquired Immunity 後天性免疫的類型,Acquired immunity： refers to the protection
3、an animal develops against certain types of microbes or foreign substance. Actively：is acquired actively when a personis exposed to microorganisms or foreignsubstances and the immune systemrespond. Passively：is acquired passively whenantibodies are transferred from oneperson to another.,2011/04/01,5
4、,Acquired Immunity,Naturally Acquired Immunity： Naturally acquired active immunity： is obtained when a person is exposed to antigens in the course of daily life. Naturally acquired passive immunity： involves the natural transfer of antibodies from a mother to her infant. Transplacental transfer： Col
5、ostrum：,2011/04/01,6,Acquired Immunity,Artificially Acquired Immunity： Artificially acquired active immunity： Results from vaccination(Ag). Immunization Vaccines. Artificially acquired passive immunity： Involves the introduction of antibodies (rather than antigens) into the body. Antiserum：(serology
6、) Globulins：(a, b and g-globulin) g-globulin：immune serum globulin.,2011/04/01,7,Terminology,Antiserum： Generic term for serum because it contains Ab. Serology： Study of reactions between antibodies and antigens. Globulins： Serum proteins, fractions are termed a, b, and g globulin. Gamma globulin (
7、globulin；immune serum globulin)： Serum fraction containing Ab.,2011/04/01,8,Serum Proteins,Figure 17.2,2011/04/01,9,Types of Acquired Immunity,2011/04/01,10,Historical Development,Pasteur observed immunity in chickens injected with weakened pathogens Von Behring received the Nobel Prize (1901) for d
8、evelopment of antitoxin Ehrlichs work led to the identification of antibodies in serum Elie Metchnikoff received the Nobel Prize (1908) for development of phagocytes.,2011/04/01,11,The Immune Response The Duality of the Immune system 免疫系統的雙重性,Humoral immunity (Antibody-Mediated)： Involves Ab produce
9、d by B cells. Defends bacteria, bacteria toxin, virus. Cell-mediated immunity： Involves T cells. Effective against bacteria and viruses located within phagocytic or infected host cells, and against fungi, protozoa, and helminths.,2011/04/01,12,獲得性 acquire,2011/04/01,13,Dual Nature of Adaptive Immuni
10、ty,T and B cells develop from stem cells in red bone marrow Humoral immunity： B cells mature in the bone marrow Chickens：Bursa of Fabricius Due to antibodies. Cellular immunity Due to T cells T cells mature in the thymus,ANIMATION Humoral Immunity: Overview,2011/04/01,14,Dual Nature of Adaptive Immu
11、nity,Figure 17.8,2011/04/01,15,Antigens and Antibodies,Antigens (immunogens)：(MW：10,000) Provoke a highly specific immune response in an organism. Most antigens are either proteins or large polysaccharides Lipids and nucleic acids usually are antigenic only when combined with proteins and polysaccha
12、rides Components of invading microbes：Capsules, cell walls, flagella, fimbriae, and toxins, coats of viruses. Nonmicrobial antigens：Pollen, egg white, blood cell surface molecules, serum proteins,2011/04/01,16,Antigenic Determinants (epitoses),Figure 17.3,Antibodies recognize and react with antigeni
13、c determinants or epitopes.,2011/04/01,17,Haptens,Figure 17.4,A foreign substance that has a low molecular weight is often not antigenic unless it is attached to a carrier molecule. These small compounds are called haptens.,2011/04/01,18,The Nature of Antibody and It Structure,Antibodies：Are protein
14、s that are made in response to an antigen and can recognize or destroy that antigen. Antigen-binding site. Valence：bivalent. Immunoglobulin： (Igs) a monomer,Figure 17.5a-c,2011/04/01,19,抗體之結構,絞鏈區hinge region,S S,木瓜脢(papain)分解位置,VL,CL,CH,VH,S-S,VH,CH,CL,VL,S-S,CH,CH,CH,CH,重鏈Heavy chain,輕鏈Light chain,
15、重鏈,輕鏈,胃蛋白脢(pepsin)分解位置,Fab片段,Fc片段,V：可變區 C：恆定區,S S,Antigen-binding site,2011/04/01,20,2011/04/01,21,Antibodies,Figure 17.3c,2011/04/01,22,(Dimer),(Pentamer),2011/04/01,23,2011/04/01,24,Major histocompatibility complex (MHC) expressed on mammalian cellsT-dependent antigens Ag presented with (self) MHC
16、 to TH cell TH cell produces cytokines that activate the B cell T-independent antigens Stimulate the B cell to make Abs,B Cells and Humoral Immunity Activation of B Cells,ANIMATION Antigen Processing and Presentation: Overview,2011/04/01,25,Activation of B Cells,Figure 17.6,2011/04/01,26,Activation
17、of B Cells,Figure 17.4,2011/04/01,27,Self-tolerance,Body doesnt make Ab against self. Differentiation between self and nonself. Clonal deletion： The process of destroying B and T cells that react to self antigens. B and T cells that interact with self antigens are somehow destroyed during fetal development, most probably during passage through the thymus.,
