五年制-3抗免疫

1、Immunity against viral infectionsSection 2 innate immunity Barrier structures Secretory molecules PhagocytesNK cells Interferon (IFN) Macrophage NK cell Innate immunity against viral infectionsInterferon（ IFN）Concept: A class of protein (glycoprotein ) produced by cells in response to viral infectio

2、n or other interferon inducers that protected other cells of same species from attack by a wide range of viruses.The activities : anti-virus; anti-tumor ; modify immune responses IFN inducers: viruses bacterial endotoxins PolyI:C, etc classification of IFNs: Hu IFN IFN- IFN- IFN-Gene chromosome 9 ch

3、romosome 9 chromosome 12 cell blood mononuclear cell fibroblasts Ag-activated T cellanti-viral + + +ActivityModify-immune + + +responses The antiviral activity of IFN: IFN cannot act directly on virus, but through induction of antiviral protein (AVP) play the antiviral activity . Mechanisms: IFN com

4、bines with specific receptor on cell surface Trigger signal transmission AVP gene actived AVP mRNA transcribed AVP synthesis. AVP mainly consists of two cell-encoded enzymes: 2,5-A synthetase, protein kinase R (PKR); dsRNA2,5-A synthetase 2,5-A activation of Rnase L degrad viral mRNAs inhibit viral

5、protein synthesis inhibition of viral replication dsRNAPKR activation of PKR phosphorylate eIF-2 ( inactivating eIF-2 ) inhibit viral protein synthesis inhibition of viral replication IFN 抗病毒作用示意图Antiviral characteristics of IFN: have no direct effect on virus: through induce cells to produce AVP ha

6、ve host species specific: IFN inhibit viral replication only in the species in which it was produced. have broad-spectrum antiviral activity: IFN inhibit the intercellular replication of a wide variety of viruses ( AVP - is a kind of enzymes ) . act in the early phase of viral infection: IFN are pro

7、duced within a few hours of the viral infection. The Immune regulation and Anti-tumor activities of IFN: Modify immune responses: - activation of macrophage - activation of NK cell - increased expression of MHC moleculesAnti-tumor activities : - inhibit the growth of certain cancer cells Macrophage:

8、 phagocytosis , control virus infection NK cell: lyse virus- infected cell directly, play an important role in early viral infection before activation of acquired immunity. produce IFN- , TNF- innate immune cell Acquired immunity I. Humoral immunity antibodys (sIgA, IgM IgG ) 1. Virus neutrilizing a

9、ntibodies : neutrilizing antibodies - antibodies formed against some surface antigens of the viruses. They can can act on free viruses and neutralize the infectivity of the viruses. Mechanisms: neutrilizing antibodies can bind to the suface proteins of the virus, and interfere with the adsorption of

10、 viruses . IgG IgM SIgA. neutrilizing antibodies: act on free viruses but cant directly kill viruses antibody- coated virus is destroyed by complement antibody- coated virus is destroyed by phagocyte Complement fixation antibody:( non-neutrilizing antibody) antibodies formed against internal components of the virus , they do not neutralize the infectivity of the virus. II. Cell mediated immunity: act on intracellular viruses . the destruction of an infected cell before progeny particles are released - an effective way of terminating a viral infection.CD8