Unit 2 - Lecture 9 Overview of the Immune System (Innate Immunity) Flashcards
What are sites of viral entry?
So in order for a virus to cause disease what must occur?
In order for a virus to cause disease:
- Gain access to a susceptible host
- Target tissue/tropism
- Evade the host’s immune defenses
- Innate immune system
- Adaptive immune system
- Cause damage/death to the host in which it replicates
What are Anaphylatoxins?
- Fragments C3a and C5a function as anaphylatoxins to bind on receptors found on innate immune cells.
- Induce degranulation, smooth muscle contraction, increased vascular permeability.
- Induce monocytes and neutrophils to adhere to endothelial cells and extravasate to sites of inflammation.
What are Cytokines?
Cytokines: Hormone-like proteins tha tcommunicate via cell-receptors to induce cell activities.
The second part of the Innate immune system is called:
Complement System
- First identified in 1890 as a component of serum that works with antibodies to destroy bacteria.
- Later discovered to be a complex group of proteins in serum that interact to facilitate a number of immune activities.
- Synthesized mainly by liver hepatocytes and constitute 5% of the serum globulin fraction.
- Linked to adaptive immunity through its interactions with antibodies.
- Also linked to innate immunity due to its recognition of pathogen-associated moleculat patterns (PAMPs).
What is involved in the external barrier Skin?
- Desquamation of skin removes bacteria (transient) that have adhered to epithelial surfaces
- Skin also secretes a number of peptides and proteins with potent anti-microbial activity (i.e., psoriasin)
Chart:
- Keratin = “waterproof” protein
- Tightly packed epithelial cells
- Specialized innate cells
- Connective tissue
- Blood Vessels
The fever response is initiated by what?
Fever Response:
- Pyrogens
- Cytokines
How are Viruses Detected?
- PAMPS: pathogen-associated molecular patterns
–-Essential for viral replication
—Not expressed in the host
- PRR: pattern recognition receptor expressed by host to detect “nonself” molecules
- —Expressed by immune cells
- –Recognize PAMPS
- –Activate innate immune responses
What are Natural Killer (NK) cells?
- First line of defense against viruses.
- Target and kill virally-infected cells and tumor cells.
- Produce cytokines that regulate immune responses (i.e., IFN-g and TNF-a):
–Stimulate dendritic cell maturation
—Activate macrophages
—-Initiate T cell responses
What is the Urogenital Tract?
- Epithelial cell barrier
- Urine
********Slightly acidic
********Flushing action
- Mucous lining
- Antimicrobial peptides
- Specialized cells (M cells) that capture antigens and microbes
What is the Coagulation System?
- Coagulation system (clotting process) activated upon severe tissue injury
- Coagulation can physically trap microbes in blood clots
- Some products are directly antimicrobial.
Describe the Gastrointestinal Tract
- Epithelial cell barrier
- Surface area of GI tract is approx. the surface area of football field
- Low pH (1-4)
- Mucus
- Digestive enzymes
- Health-enhancing intestinal bacteria
- Inductive immune sites
- Specialized cells (M cells) that capture antigens and microbes
In the Nonspecific Immunity what is involved with the Natural Killer Cells?
- NK cells recognize
Cells that undergo a declined expression of MHC molecules or
Cells that contain surface antigens displayed by some tumor cells or
Virally infected cells
- Once activated, NK cells release pore-releasing proteins
***Perforins
***Granzymes (proteases)
***Chemokines
- NK cells can bind to cells containing bound antibodies through recognition of Fc region of antibodies
What are Chemokines?
Chemokines: Subgroup of cytokines that cause cells to move towards the site of injury or infection.
Alick Isaacs and Jean Lindenmann performed what type of experiment?
Interference Experiement
Substance secreted by cells “interfered” with viral infection.
Interferons were first discovered.
What is the Inflammatory Response?
- Tissue damage causes release of vasoactive and chemotactic factors that trigger a local increase in blood flow and capillary permeability.
- Permeable capillaries allow an influx of fluid (exudate) and cells
- Phagocytes migrate to site of inflammation (chemotaxis)
- Phagocytes and antibacterial exudate destroy bacteria.
What is involved in the generation of antimicrobial Speicies in Phagocytes?
- Respiratory burst: O2 consumed by phagocytes (neutrophils, macrophages) is converted within phagosomes to toxic reactive oxygen species (ROS)
- Occurs via action of the enzyme NADPH phagosome oxidase.
- Some pathogens possess non-oxidant defenses to mediate survival when in the phagosome.
- Inducible nitric oxide synthetase (iNOS): oxidizes L-arginine to nitric oxide
- Nitric oxide (NO) by itself has antimicrobial activity.
- NO can also combine with superoxide to from even more potent antimicrobial compounds.
Describe the summary of Innate Immunity:
What are the different Pathways?
What are the different things involved?
Pathways:
1. Classical
2. Alternative
3. Lechin
- Complement system comprises a group of serum proteins, many of which circulate in an inactive form.
- Complement activation occurs through the classical, alternative, and lectin pathways.
- Classical pathway is “adaptive” in that it requires antibody binding.
- Alternative and lectin pathways are “innate” in that they are activated by recognition of PAMPS.
- Three pathways converge at the generation of a molecular complex that causes cell lysis.
- Complement system also mediates opsonization of bacteria, activation of inflammation, and clearance of immune complexes.
- Innate immunity is found in many organisms- vertebrates, invertebrates, and even plants
What are defensins in Innate Antiviral immunity?
- Defensins inctivate enveloped virus particles
- Defensins can block fusion of viral membranes with endosomes
A. Effects on the virion
B. Effect on the HIV infected cell
C. Effect on influenza-virus-infected cell
What is Apoptosis with viral infections?
Apoptosis:
- Programmed dell death (PCD)
- morphological changes
- Viruses can trigger PCD, counteract PCD, or do both
— activation of caspases
– apoptosis and disease severity
- Halt virus spread
- Viral dissemination
What are Mucous Membranes?
Where are they located?
What is the purpose of them?
- Gastrointestinal, respiratory, and urogenital tracts.
- Saliva, tears, and mucous secretions wash away microbes.
- Antibacterial and antiviral substances (lysozyme, defensins, surfactants)
- Cilia in respiratory tract propel mucus-entrapped microbes from body.
- Stomach contains acid and digestive enzymes.
- Normal flora colonize mucosal surfaces to out-compete pathogenic microbes for space and nutrients.
