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Immunity to microbes (mechanisms of defense against viral, parasitic and fungal infections)

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Presentation on theme: "Immunity to microbes (mechanisms of defense against viral, parasitic and fungal infections)"— Presentation transcript:

1 Immunity to microbes (mechanisms of defense against viral, parasitic and fungal infections)

2 Goal bacteria - extracellular - intracellular viruses parasites - protozoa - helmints fungi To understand basic principles of defense against infections induced by:

3 Viruses - unable to replicate outside cells Simple structure (subcellular level) Obligate intracellular agents - enter cells via receptors - acute Infections - chronic (active and latent) - damage of cells in which they replicate Induce diseases through - induction of immune response

4 Mechanisms of defense against viruses - inhibition of infection and induction of antiviral state type I interferons (IFN-α and β) - killing of infected cells (NK cells) Mechanisms of innate immunity

5 Antiviral action of type I interferons Expression of class I MHC molecules Expression of enzimes that inhibit viral replication Uninfected cells Infected cells Protection from infection Killing of infected cells by CTLs

6 Destruction of infected cells by NK cells

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9 - neutralization (IgG and IgA), ADCC (IgG) and opsonization (IgG) Mechanisms of defense against viruses Mechanisms of adaptive immunity Humoral immunity B cells and antibodies Cell-mediated immunity

10 Neutralization of viruses

11 Protective mechanisms of antibodies

12 - neutralization (IgG and IgA), ADCC (IgG) and opsonization (IgG) - activation of CD8 + T cells and and B cells (CD4 + helper T cells) CD8 + and CD4 + T cells Mechanisms of defense against viruses Mechanisms of adaptive immunity Humoral immunity B cells and antibodies Cell-mediated immunity - killing of infected cells (CD8 + T cells)

13 Mechanism of killing by CTLs

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18 perforin CD8 + CTL Target cell apoptosis granzymes Mechanism of killing by CTLs

19 CD8 + CTL Target cell FasLFas apoptosis Mechanism of killing by CTLs

20 Mechanisms of innate and adaptive immunity against viruses

21 - antigenic variation (influenza virus, HIV...) Mechanisms of immune evasion Mechanisms of defense against viruses

22 Antigenic variations of influenza virus

23 - antigenic variation (influenza virus, HIV...) Mechanisms of immune evasion Mechanisms of defense against viruses - inhibition of antigen processing and presentation (many viruses)

24 Inhibition of antigen processing and presentation by viruses

25 - antigenic variation (influenza virus, HIV...) - inhibition of antigen processing and presentation (many viruses) - inhibition of immune response (many viruses) Mechanisms of immune evasion Mechanisms of defense against viruses

26 Inhibition of immune response through production of virokines and viroreceptors

27 - antigenic variation (influenza virus, HIV...) - inhibition of antigen processing and presentation (many viruses) - inhibition of immune response (many viruses) - infection of immune cells (HIV...) - establishment of latency (HSV, HIV...) - inhibition of apoptosis (Herpes and Pox viruses...) Mechanisms of immune evasion Mechanisms of defense against viruses

28 - tissue damage due to CD8 + CTL activity (HBV...) - immune complexes formation (HBV...) - „molecular mimicry” (many viruses and various autoimmune diseases) Injurious effects of immune response Mechanisms of defense against viruses

29 Parasites - protozoa (unicellular) – intra- and extracellular agents - complex eukaryotic organisms - helmints (multicellular warms) – extracellular agents - most common infectious diseases (30% of world population) - complex life cycles - constant exposure (endemic areas) - need for vaccines (immunoparasitology) - direct exposure or via vectors - often induce chronic infections

30 Mehanisms of innate immunity Protozoa and helmints – mostly resistant - complement and phagocytosis (protozoa) - eosinophils and macrophages (helmints) Mechanisms of defense against parasites

31 -IFN-γ production and macrophage stimulation (CD4 + T H 1 cells) - Leishmania sp. Protozoa Helmints - cytotoxicity (CD8 + T cells) – Plasmodium sp. Mehanisms of adaptive immunity - antibodies (B-cells) – Entamoeba sp., Plasmodium sp. B-cells, CD4 + T H 1 and CD8 + T cells B-cells and CD4 + T H 2 cells - stimulation of eosinophils (IL-5 and IgE) - stimulation of B-cells to produce IgE (IL-4) - degranulation of mast cells (IgE) Mechanisms of defense against parasites

32 Immunity against helmints (T H 2 response)

33 Immunity against helmints (function of eosinophils)

34 Injurious effect of immune response Mechanisms of immune evasion - granuloma formation and fibrosis (Schistosoma sp.) - alteration of surface antigens (Trypanosoma sp....) - complement resistance (many parasites) -“concealing” – cysts (Toxoplasma sp.), residence in gut (intestinal parasites) - immune complex formation (Plasmodium sp.) - existence of different forms/stages (Plasmodium sp...) Mechanisms of defense against parasites

35 Fungi - yeast (unicellular) - molds (multicellular) - extracellular agents (some survive phagocytosis) - most systemic infection - opportunistic some endemic (dimorphic fungi) - risk factor - immunodeficiency (neutropenia) - local and systemic mycoses

36 Mechanisms of defanse against fungi Fungi – mostly susceptible Mechanisms of innate immunity - phagocytosis (neutrophils) Mechanisms of adaptive immunity - macrophage and neutrophil activation (CD4 + T H 1 and T H 17 cells) Injurious effect of immune response - granuloma formation and fibrosis (Histoplasma capsulatum) Mechanisms of immune evasion - inhibition of phagocytosis (C. neoformans...) - complement Cell-mediated immunity

37 Thanks for your attention! Questions?


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