immunity to microbes (mechanisms of defense against viral, parasitic and fungal infections)
DESCRIPTION
Immunity to microbes (mechanisms of defense against viral, parasitic and fungal infections). Goal. To understand basic principles of defense against infections induced by :. ba c teri a - e x tracel l ular - intracel l ular. virus es. para sites protozoa helmint s. fungi. Virus es. - PowerPoint PPT PresentationTRANSCRIPT
Immunity to microbes
(mechanisms of defense against viral, parasitic and fungal infections)
Goal
bacteria - extracellular- intracellular
viruses
parasites- protozoa- helmints
fungi
To understand basic principles of defense againstinfections induced by:
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
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
Antiviral action of type I interferons
Expression ofclass I MHC molecules
Expression of enzimes that inhibit viral replication
Uninfected cells
Infectedcells
Protection frominfection
Killing of infected cells by
CTLs
Destruction of infected cells by NK cells
Destruction of infected cells by NK cells
Destruction of infected cells by NK cells
- 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
Neutralization of viruses
Protective mechanisms of antibodies
- 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)
Mechanism of killing by CTLs
Mechanism of killing by CTLs
Mechanism of killing by CTLs
Mechanism of killing by CTLs
Mechanism of killing by CTLs
perforin
CD8+ CTLTarget cell
apoptosis
granzymes
Mechanism of killing by CTLs
CD8+ CTLTarget cell
FasL Fas apoptosis
Mechanism of killing by CTLs
Mechanisms of innate and adaptive immunity against viruses
- antigenic variation (influenza virus, HIV...)
Mechanisms of immune evasion
Mechanisms of defense against viruses
Antigenic variations of influenza virus
- antigenic variation (influenza virus, HIV...)
Mechanisms of immune evasion
Mechanisms of defense against viruses
- inhibition of antigen processing and presentation (many viruses)
Inhibition of antigen
processing and
presentation by viruses
- 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
Inhibition of immune response through production ofvirokines and viroreceptors
- 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
- 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
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
Mehanisms of innate immunity
Protozoa and helmints – mostly resistant
- complement and phagocytosis (protozoa)
- eosinophils and macrophages (helmints)
Mechanisms of defense against parasites
-IFN-γ production and macrophage stimulation (CD4+TH1 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+ TH1 and CD8+ T cells
B-cells and CD4+ TH2 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
Immunity against helmints
(TH2 response)
Immunity against helmints(function of eosinophils)
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
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
Mechanisms of defanseagainst fungi
Fungi – mostly susceptible
Mechanisms of innate immunity
- phagocytosis (neutrophils)
Mechanisms of adaptive immunity
- macrophage and neutrophil activation (CD4+ TH1 and TH17 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
Thanks for your attention!
Questions?