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28 Cards in this Set

  • Front
  • Back

The vertebrate immune system has 2 parts:

Innate immune system (old, basic, reliable)



Adaptive (Acquired) immune system (newer, highly specialized and sophisticated)

What are the biggest differences between the innate and the adaptive immune systems?

Innate:



First line of defense


Present in all animals (evolutionarily conserved)


Always ready and rapidly deployed


Broad range (protects against classes of viruses)


No enhancement or memory



Adaptive:



Present only in vertebrates


Requires selection of lymphocytes, therefore delayed response - highly diverse


Very individualized - recognizes specific molecules (antigen specific) and involves gene rearrangement of highly specific receptors


Fine tuned, learns and has memory - remembers what to do when it comes into contact with an agent for the second time

What are the three types of communication within the immune system?

1. Cytokines (interleukins, interferons, colony-stimulating factors, growth factors/necrosis factors)


2. Other signalling molecules (monoamines, eicosanoids)


3. Cell-cell contact (via receptors)

What are interleukins?

Abbreviation: IL


A type of cytokine


Produced by leukocytes (WBC's)


Act on other leukocytes (communication between WBC's)

What are interferons?

Abbreviation: IFNs


A type of cytokine


Important in coordinating immune response to infections, especially viral infections

What are colony-stimulating factors?

Abbreviation: CSFs


A type of cytokine


Promotes proliferation and differentiation of leukocyte precursors

What are eicosanoids?

Lipid-based mediators such as prostaglandins and leukotrienes



Signalling molecules used in communication in the immune system

How do lymphocytes and other cells communicate in the immune system?

Through cell-cell contact



Via receptors which induce intracellular programs


= "signalling"

Which threats are extracellular?

Bacteria


Fungi


Parasites



*sometimes see viruses in extracellular fluid, but they do not replicate there

Which threats are intracellular?

Bacteria


Viruses


Parasites

What are some innate effectors for extracellular threats?

Complement activation


Phagocytosis by phagocytes


Extracellular killing (release of substance that kills cells)

What is an innate effector for intracellular threats?

NK cell cytotoxicity - do not need a specific receptor

What are some adaptive effectors for extracellular threats?

B cells and helper T cells


Antibodies (humoral)

What are some adaptive effectors for intracellular threats?

Cytotoxic T cells (cell mediated)


Macrophage and Helper T cells (cell mediated)

What are the 3 major components of the Innate immune system:

Serum proteins


- complement


- acute phase proteins (CRP)



Professional phagocytes:


- neutrophils


- macrophages



Natural Killer Cells

Which cells are key for the adaptive immune system? Why?

Lymphocytes



They express clonally distributed receptors for antigens or potential antigens



Individually each clone expresses only one specific antigen receptor



But as a population, the lymphocytes express >5 x 10⁷ different antigen receptors



= "clonal expansion" - lymphocytes that have the right antigen receptor clone in response to the antigen being present (this is why the adaptive immune response takes time)

How does memory in the adaptive immune system work?

The adaptive immune response relies on the identification and expansion of the clone that expresses the antigen receptor that can bind the specific relevant antigen best.



The second time the immune system responds to an antigen:



- higher response (more antibodies since they were cloned the first time the pathogen was encountered)


- faster response (same as above)


- prolonged response (high levels of antibodies continue on for a longer period of time)

What is an epitope?

The specific piece of the antigen that the antibodie binds to



Recognized by antibodies, B cells or T cells

How is specificity in the adaptive immune response achieved?

Receptors on B and T cells only bind a single antigen (epitope)



The receptors undergo genetic rearrangements so that there are nearly an unlimited amount of different receptors that can bind different epitopes

How are T cells able to carry out different types of immune responses?

At primary immunization/infection, antigen-presenting cells (APC's) ingest pathogens and present pathogen-derived antigens to "naive" T cells



The T cells then differentiate and divide rapidly to give different immune responses

What are some of the immune responses initiated by effector T cells and which types of cells cause which responses?

CD8 T-cells are activated, and differentiate into:


1. Cytotoxic killer cells: Destroy virus-infected cells



CD4 T-cells are activated and differentiate into:


1. Th1 Cells: Activate macrophages to kill ingested bacteria


2. Th1 and Th2 cells: Activate B cells to produce antibodies


3. Th17 cells: Stimulate inflammation (neutrophils)


4. Treg cells: suppress activation to self-antigen (self-tolerance)

How are B cells different from T cells?

B cells also have receptors for antigens but once they bind an antigen, they interact with certain T cells and then differentiate into plasma cells



These plasma cells secrete antibodies into lymph and blood

What are antibodies?

A soluble form of the B-cell receptors

Name 3 immune response mechanisms of antibodies:

Neutralization


Opsonization


Complement activation

What is neutralization?

Antibodies bind to toxins or viruses so the toxins can no longer bind to specific receptor on host cells (therefore they are "neutralized")



Occurs outside the cell

What is opsonization?

Antibodies bind to bacteria


This enhances phagocytosis of pathogens by macrophages

What is complement activation?

Similar to opsonization



IgM or IgG antibodies bind to a pathogen and this complex activates a complement fragment



Macrophages/phagocytic cells have receptors for complement fragments so this leads to more efficient phagocytosis of pathogens

At which specialized sites do adaptive immune responses arise?

Lymph nodes


Spleen


Mucosa-associated lymphoid tissue (MALT)


(e.g. tonsils)