the immune system Flashcards
what are the 2 types of immunity that are immune system consists of?
-innate immunity
-adaptive immunity
what is innate immunity? what are the 2 types of responses?
non-specific and fast response:
-barriers (physical and chemical)
-internal defenses
in innate immunity, what are the different types of internal defences?
-recognition of traits shared by broad ranges of pathogens, using a small set of receptors
-white blood cells (phagocytic and non-phagocytic)
-antimicrobial peptides
-inflammatory responses
-rapid response
what is adaptive immunity?
acquired immunity
-specific and slower response
-humoral and cell-mediated response
-recognition of traits specific to particular pathogens, using a vast array of receptors
who has innate immunity?
all animals
who has acquired immunity?
vertebrates
what are innate immunity barrier defences?
-skin
-mucous membranes
-secretions
what are innate immunity internal defences?
-phagocytic cells
-natural killer cells
-antimicrobial proteins
-inflammatory response
in adaptive immunity what is humoral response?
-antibodies defend against infection in body fluids
in adaptive immunity what is cell-mediated response?
cytotoxic cells defend against infection in body cells
in innate immunity, what is the first line of defence?
Physical and chemical barriers.
what are examples of physics; and chemical barriers?
-skin, mucous membranes (lining of digestive, respiratory and genitourinary tract)
-sweat contains acids that inhibit bacterial growth
-saliva, tears and mucous wash away pathogens and contain lysozyme to destroy bacterial cell wall
what is the second line of defence of innate immunity?
inflammatory response
what happens during inflammatory response? When does it happen?
-when tissue is damaged or microorganisms enter (or both)
-damaged cells or microorganisms release chemicals that:
increase permeability and blood flow
bring clotting factors and phagocytic cells to the cite
what are the chemicals released by the damaged cells during the inflammatory response? what do they allow for?
-histimines
-cytokines
-prostaglandins
these chemicals allow for the increase of blood flow to site, dilating blood vessels and increasing permeability of capillaries
what are phagocytic white blood cells?
white blood cells that ingest invading microbes
what are the types of phagocytic blood cells?
1) neutrophils
2) macrophages
how do phagocytic white blood cells kill pathogens?
what are the non-phagocytic white blood cells? what do they each do?
1) eosinophils: release chemicals to destroy parasites
2) mast cells: release histamine
3) natural killer cells: destroy virus-infected cells and cancer cells by causing cell lysis
what chemicals kill the cell by cell lysis?
perforin and granzyme
what are the two types of antimicrobial peptides?
1) complement
2) interferon
what are complement antimicrobial peptides?
-over 30 serum proteins
-involved in a cascade of steps which lead to cell lysis of a bacterium or an infected cell
what does an interferon do?
-secreted by virus infected cells
-prevents cell-cell spread of the virus and inhibits viral production
-like an alarm
how are interferons made?
they are secreted by viral cells
how do interferons prevent the spread of virus?
what are the key players in the adaptive/acquired immunity system?
antigens
antibodies
lymphocytes
antigen presenting cells
what are the 2 types of lymphocytes?
-B-cells
-T-cells (T-helper cells and cytotoxic T-cells)
what are the types of antigen presenting cells?
-macropages
-dendritic cells
-B-cells
which antigen presenting cell is present in both immune systems?
macrophages
what are antigens?
-protein or a polysaccharide that lymphocytes are reactive to
-
how do antigens work?
-each antigen has a unique structure that a specific T-cell or B-cell receptor will bind to
-antigens are found on the surface of viruses, virus-infected cells, bacteria, fungi, protozoa, pollen or transplanted tissue
what do lymphocytes do?
mediate cell response
what do B-cells do?
-involved in humoral response
-produce antibodies
-mature in the bone marrow
what do T-cells do?
-involved in cell mediated response
-mature in the thymus
what do mature T-cells and B-cells have on their surfaces?
antigen receptors
what are the 2 types of B-cells?
-plasma cell
-memory B-cell
what’s a plasma cell?
effector B-cells that produce antibodies
what’s a memory B-cell?
-long lived and will act in future infections
-has antigen receptor
what is the antibody structure?
-compromised of 4 polypeptide chains (2 identical light chains, 2 identical heavy chains)
-each chain is composed of a variable region and a constant region
what is the variable chain of the antibody?
-amino acid sequence varies from antibody to antibody
-binds to specific antigen
what is the constant chain of the antibody?
involved in antigen disposal
what is another name for antibodies?
immunoglobulins
what does an antibody look like?
what are the 2 types of T-cells?
-cytotoxic T-cells
-Helper T-cells
what do cytotoxic T-cells do?
release perforin and grandzymes to kill infected cells
what do helper T-cells do? give an example
release chemicals to activate other cells, which enhances immune response
-ex: Help B-cells become activated
what is clonal selection?
response to entry of pathogen
what are the steps of clonal selection?
1-antigen enters body and lymphocyte with matching receptor binds to the antigen
2-lymphocyte becomes activated: divides and differentiates to produce thousands of cells specific for that region
3-two clones are produced:
-effector cells: short lived and actively destroy antigen
-memory cells: long lived and will respond to future entry by same antigen
which type of cell is linked to immunological memory?
memory cells (B cells)
what is the point to having memory b-cells and plasma/effector cells?
Once B-cells are activated, they become plasma cells that produce antibodies in response to an antigen. Or they become memory cells that remember the antigen so your immune system can quickly identify and fight it in the future
what do antigen presenting cells do?
-phagocytize pathogens and present antigen fragments on their surface
in antigen presented cells, where are the antigens presented?
within MHCII
what is MHC?
major histocompatibility complex
what is the purpose of MHC?
-present antigen to T-cells
-T-cells will only interact with antigen when it is presented in MHC
what are the 2 types of MHCs?
class I: present on most nucleated cells
class II: present on antigen presenting cells only
how are T-cells activated?
interacting with antigen/MHC
what type of MHC do cytotoxic T-cells interact with?
interact with cells expressing MHC I+ antigen
what type of MHC do helper T-cells interact with?
interact with cells expressing MHC II+ antigen
which type of T-cells can interact with APC?
helper T-cells
true or false, clonal selection occurs only for T-cells
false, it occurs for both T-cells and B-cells
what is the humoral response?
- B-cells specific for an antigen are activated to make plasma cells
- Plasma cells produce antibodies (also specific for the antigen)
- Antibodies bind to free, intact antigens in body fluids
How are b-cells activated?
by binding to an antigen that its receptor specifically interacts with, which leads to clonal selection
what are the three different ways in which antibodies can dispose of antigens?
1) neutralization:
-antibodies bound to antigen on the surface of a virus neutralize it by blocking its ability to bind to a host cell
-coat bacteria to enhance phagocytosis (opsonization)
2) opsonization:
-clumping of viral particles or bacterial cells to enhance phagocytosis
3) complement fixation: binding of antibody to foreign cell initiates complement cascade which results in cell lysis
what are cytotoxic T-cells activated to do?
Cytotoxic T-cells specific for an antigen are activated to destroy cells
containing the antigen (infected cells!).
what immune responses do cytotoxic T-cells mediate?
i. intracellular antigens (will be presented on MHC)
ii. Fungi, protozoa and parasitic worms
iii. Transplanted tissues and cancer cells
what are the steps to the cell-mediated response of cytotoxic T-cells?
how is the humoral and cell mediated pathway linked?
through T-helper cells
which immune response fights against intracellular pathogens and cancer?
cell-mediated response
which immune response fights against extracellular pathogens in blood and lymph?
humoral response
what steps of the adaptive immune systems?
1) APC phagocytizes the pathogen and presents antigen on its surface cradled within MHC II
2) Helper T-cell with correct receptor interacts with antigen/MHC II:
-interaction is enhanced by CD4, an accessory protein on helper T-cells
3) Two clones of the T helper cell are produced:
-effector cells: secrete interleukin 2 (IL-2)
-Memory T cells:
.ready to respond to a subsequent exposure
what is the link between the B-cells and the cytotoxic T-cells?
have the same antigen receptor as the T-helper cell that activates them. they both get activated by t helper cells
what are the two clones of the T helper cells that are produced during the adaptive immune response
memory T-cells and effector cells
what is IL-2
cytokine which activates B-cells, cytotoxic T-cells and helper T-cells
what happens during the first response (immunological memory)
-only 1 of each cell that is specific for antigen that need to be activated to produce more
what happens during the second response (immunological memory)
many memory cells available and ready to be activated (response is faster)
Which one is the primary and which one is the secondary response?
First one is primary response
what happens during the secondary response?
-memory cells are activated
-antibody concentration peaks 2-7 days after exposure
-more effector cells are produced faster
what happens during primary response?
- First exposure to antigen
- Peaks 10-17 days after exposure
- After response memory cells stick
around for next exposure
Which one is primary response and which one is secondary
First graph is primary
what are the subcategories to immunity?
-natural or artificial
-active or passive
what is active immunity?
- Conferred by recovery from an infectious disease Immune memory! (immunity lasts)
- Depends on an individual’s own immune system Naturally: recovering from infectious disease Artificially: vaccination
what is passive immunity?
- Antibodies transferred from one individual to another (immunity does not last)
Naturally: when mother transfers antibodies to the fetus across the placenta or to
the infant while nursing
o Temporary protection (weeks – months)
Artificially: by injecting antibodies into an individual (ex: Rabies antibodies)
what are vaccines?
-Vaccines are weakened versions of a pathogen that do not cause disease but can induce an immune response (ex: inactivated toxin, killed microbe or parts of a microbe)
- A vaccine gives you immune memory without making you sick!
why can we get sick by the same virus more than once?
viruses can mutate so that our immune systems no longer recognize their antigens
what is an allergy?
Hypersensitivity of the immune system to an allergen after an initial exposure caused
an immune response. (no reaction at first exposure)
what happens during subsequent exposures for allergies?
Mast cells with attached antibodies will circulate in the blood and react quickly with allergen upon subsequent exposures
what are the steps to the formation of an allergy?
1) initial exposure to allergen. Leads to production of IgE antibodies specific for allergen
2) IgE antibodies will bind to receptors on surface of mast cells
3) subsequent exposure will result in allergen binding to antibodies, cross linking them and the release of histamine
what happens to the immune system for autoimmune disorders?
-immune system acts against itself
-a failure to recognize self
why is our immune self-tolerant?
because lymphocytes bearing antigen receptors for self-molecules are destroyed (elimination of self-reactive B-cells), but errors in this process lead to autoimmune disease
what are immunodefencies?
an individual is deficient in either humoral or cell-mediated defences or both (immune system doesn’t work properly)
what protein helps cytotoxic T-cells?
CD8
what type of MHC do all cells with a nucleus have?
MHC I
which cells have memory cells
lymphocytes
what is IL2?
cytokine that t helper cell releases, which activates itself, B-cells and cytotoxic T cells
what is CD8?
cytotoxic T cell
what activates clonal selection for B cells and cytotoxic T cells?
the release of cytokines from t helper cells activates them (especially for the first response) which makes them go through clonal selection
what is the lymphocyte in innate immunity?
natural killer cells
which APC are involved in both innate and specific immunity?
macrophages
why do all nucleated cells have MHC?
if they’re infected, they can present these pathogens on their surface, so that cytotoxic cells can attack
what is the difference between the cytotoxic T cells memory cells and effector cells?
-memory cells: last longer
-effector cells: SHORT LIVED
