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BM108 🧬 > innate and aquired immunity > Flashcards

innate and aquired immunity Flashcards

1
Q

what is innate immune systems?

A
  • they’re non-specific immune systems that protect against foreign cells or substances without having to recognise their specific identity
  • its an inherited ability which doesn’t require prior exposure to invaders
  • it recognises a general, conserved property that marks the invader as foreign
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2
Q

how does the body surface work as part of the innate immune system?

A
  • its the initial line of defence
  • few microorganisms can penetrate the intact body surface
  • skin glands secrete antimicrobial molecules
  • mucus us sticky so it traps invaders and is also antimicrobial
  • stomach acids destroy invaders
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3
Q

how do phagocytic cells act as part of the innate immune system?

A
  • phagocytes engulf and destroy particles by endocytosis

- they’re present in all classes of animals and are the most fundamental and ancient of all the body defences

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4
Q

what are the types of eukaryotic phagocytic cells?

and what do they do?

A

neutrophils and natural killer cells

  • basophils secrete herparin and histamine
  • NK cells recognaise general features of cancer or non-virus infected cells and kill them
  • dendric cells perform macrophage funtions
  • mast cells release histamine
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5
Q

how does inflammation work in innate immnity?

A
  • an innate local response to infection or injury
  • the inflammation destroys or inactivates forgein invaders and clears the area of dead cells and sets the stage for tissue repair
  • key cellular components of this process are phagocytes, mainly neurolphils, macrophages and dendric cells as well as mast cells
  • inflammation is induced and regulated by cytokines
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6
Q

what are cytokines and what do they do?

A
  • theyre lots of different types of proteins produced by a variety of cells
  • they act on cells which have a receptor for the cytokine
  • theyre produced by most immune cells- innate [macrophages, eosinophils, mast cells and basophils], specific cells [ lymphocytes]
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7
Q

what induces vascular changes to the area of inflammation?

A

injured cells, mast cells and neutrophils send signals to induce vascular changes

  • the increased blood flow to the area increases delivery of benefitial proteins and leukocytes
  • the increased vascular permeability allows the plasma proteins to gain entry to interstitial fluid
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8
Q

what happens once phagocytes are in the area of infection?

A

they encounter microbes and relase inflammatory mediators that bring in even more phagocytes

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9
Q

what happens is tissue repair isnt perfect?

A

a scar forms

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10
Q

what are the 2 types of antimicrobial proteins?

A

interferon- they inhibit viral replication inside the host cells and are non-specific to a particular virus

complement- they kill microbes without phagocytosis and use membrane attack complex (MAC) to create channels in the microbial plasma membrane and cause the membrane to burst

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11
Q

what are PAMPs what do they do?

A
  • PAMP= pathogen-associated molecular pattern
  • innate immunity depends on a recognition of a general molecular features common to many types of pathogens or PAMPs
  • PAMPs have conserved molecular features because the structures are vital to the survival of the pathogen
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12
Q

what is the history of discovery for PAMPs?

A

in 1985, nusslein-volhard and weischaus discovered Toll-1, a gene needed for dorsalventral development in the fruit fly drosophila melengogaster
in 1996, toll-1 was found to give flies the ability to fight off fungal infections

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13
Q

where are toll proteins found?

A

toll proteins are found in membranes of macrophage, dendric and other immune cells

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14
Q

what is the function of toll cells?

A
  • they funtion to recognise and bind to ligands with PAMPs such as:
  • lipopolysaccharide
  • other microbial lipids and carbohydrates
  • viral and bacterial neucleic acids
  • a bacterial flagellum protein
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15
Q

what happens when a toll protein on an immune cell binds a PAMP ligand?

A

second messengers are generated, triggering a cytokine secretion
- these stimulate the activity of other leukocytes of the innate immune response, some also activate cells of the acquired immune response

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16
Q

what family are the toll-linked receptors classed as?

A

toll-like receptors (TLRs) as many are membrane bound receptors

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17
Q

other things about TLRs

A

toll-4 mice are hypertensive to LPS injections and have trouble fighting bacterial infections, similar proteins have been found in plants, so TLRs may be one of the first immune defense mechanisms to ever evolve

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18
Q

what are some important interferons?

A

interferon alpha- lymphoblastoid cells
interferon beta- fibroblasts, macrophages ect - theyre stimulated by abortively replicating the virus
interferon gamma- produced by stimulated NK cells and T-cells, they inhibit viral activity, enhance the activity of NK cells and activate macrophages which help to enhance phagocytosis

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19
Q

what is aquired immunity?

A

it is immunity which is learnt as a response to past infections and exposure to infective organisms

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20
Q

where are the lymphocytes in the body?

A
  • lymphocytes circulate in blood but most of them are in organs of the lymphatic system
  • a network of lymphatic vessels collects lymph and returns the fluid to blood plasma
  • primary lymphoid organs: where lymphocytes differentiate into mature immature cells, supply mature lymphocytes to secondary lymphoid organs where the lymphocytes multiply
  • lymphocytes circulate through lymphoid organs, interstatial fluid and back to lymphatic system- increasing the chance they will encounter their antigen
21
Q

what are the types of lymphocytes?

A
  • b-cells
  • t-cells
  • NK cells
22
Q

what are b-cells?

A

theyre a type of lymphocyte which mature in bone marrow
some form plasma cells that synthesize and secrete antibodies
humoral immunity

23
Q

what are t-cells?

A
  • they mature in the thymus gland
  • cytotoxic t-cells directly kill infected, mutated or transplanted cells
    helper t-cells help in activating b-cells and cytotoxic t-cells
    cell-mediated immunity
    memory
    t-cells are also the basis of vaccinations
24
Q

what are NK cells?

A

also known as natural killer cells, theyre similar to t-cells and perform non-specific actions as well as specific ones

25
Q

what are the 3 stages of aquired immunity?

A
  1. recognition of antigen
  2. activation of lymphocytes
  3. attack against antigen
26
Q

what happens in stage 1 of aquired immune response?

A

recognition of the antigen

  • during its development, each lymphocyte synthesised a membrane receptor which can bind to a specific antigen
  • antigens which bind to a lymphocyte receptor are recognised by the lymphocyte
  • each lymphocyte is specific for just one type of antigen
27
Q

what happens in stage 2 of aquired immune response?

A

activation of lymphocytes

  • upon binding to the antigen, the lymphocyte undergoes cell division to make clones
  • clones act as plasma cells carrying out the attack and as memory cells for future attacks
28
Q

what happens in stage 3 of an acquired immunological response?

A

attack against antigen

  • activated b-cells differentiate into plasma cells, secreting antibodies (these recruit and guide other molecules and cells that perform the actual attack)
  • activated cytotoxic t-cells carry out the attack, directly attacking and killing antigen-bearing cells
  • once the infectiuos pathogen is eliminated, plasma cells and cytotoxic cells die by apoptosis to prevent excessive immune response
  • memory cells stay, awaiting future invasions by the same pathogen
29
Q

what happens with b-cells and humoural activity?

A
  • the b-cells are activated by antigens and helper t-cell cytokines
  • they proliferate into plasma cells which make antibodies
  • major defense against bacterial cells, viruses and other microbes in the extracellular fluid and against toxins
30
Q

what are antibodies?

A

theyre part of the immunoglobin protein family

they’re all made of 4 interlinked polypeptides with 2 long, heavy chains and 2 short, light chains

31
Q

what are the 5 classes of immunoglobin in mammals?

A 
Igm
IgG
IgA
IgD
IgE

all vertebrates have IgM

32
Q

what are the most abundant immunoglobins in mammals?

A

IgM and IgG

they provide the bulk of specific immunity against bacteria and viruses in extracellular fluid

33
Q

what do IgE immunoglobins do?

A

they participate in defenses against multicelluallar parasites and allergenic response

34
Q

what does IgA do?

A

it is secreted by plasma cells in the linings of the GI, respiratory and genitourinary tracts
this is to act locally in these areas of the body
its also a major anybody in milk

35
Q

what is the function of IgD?

A

its unclear

36
Q

what are the variable and constant regions of B-cells?

A

theyre as the name suggests:

  • the variable region varies among different B-cells, specifically recognises the antigen
  • Fc domain is identical for given class
37
Q

what is humoral immunity?

A

it is the complicated word for activated B-cells

  • they’re divided up into plasma and memory cells
  • the offspring of this lymphocyte all express the same receptor
38
Q

how do antibodies inactivate the pathogen?

A

by:

  • opsonization- link the pathogen to non-specific immune cell to trigger attack
  • form complexes which are then destroyed by phagocytes
  • block binding sites in viruses (probably the most important feature of an antibody)
39
Q

what is cell mediated immunity?

A

its an immune responsse that activates macrophages and NK cells and t-cells

  • t-cells carry in the specific regions on themselves that differ from other t-cells
  • t-cells cant combine with antigen complexes unless complexed with MHC class I receptor
40
Q

what are MHCs?

A 
Major Histocompatibility Complex 
class I is found on all major body cells but ethrocytes
class II is found on antigen-presenting cells (APCs), macrophages, b-cells and dendric cells
CD4 on helper t-cells bind to class II MHCs
41
Q

what are antigen-presenting cells?

A
  • (ACPs) are cells that can process a protein antigen, break it down into peptides and present it in conjunction with class II MHC molecules on the cell surface where it may interact with appropriate T cell receptors.
42
Q

what are the stages of antigen-presenting cells?

A
  • macrophages, b-cells and dendric cells present antigens next to class II MHCs
  • the antigen is phagocytized by macrophage and is digested into fragments to epitones
  • fragment MHC complex is transported to the cell surface
  • specific helper t-cells bind to complex with CD4 protein helping link
43
Q

what is essential for helper t-cell activation?

A

antigen-presenting cells (APCs) and costimulus

cytokines IL-1 and TNF are also secreted by APCs to stimulate the attached helper cell

44
Q

what is involved in antigen presentation to cytotoxic t-cells?

A
  • class I MHC is needed
  • antigens that complex with class I MHC cells are made within body cells
  • virus-infected and cancerous cells make unusual proteins
  • the complexed fragments are then sent to the plasma membrane, cytotoxic t-cells then bind to the complex and release chemicals that kill infected or cancerous cells
45
Q

what is the role of cytotoxic t-cells?

A

they bind to the surface of a virus-infected cell and kill them

46
Q

what are the steps of cytotoxic t-cells killing virus-infected cells?

A
  1. the cytotoxic t-cell binds on to the surface of a virus-infected cell
  2. a helper t-cell binds to a macrophage that has phagocyzed the same type of virus. the helper t-cell then proliferates and binds to cytotoxic t-cells. the helper t-cell secretes IL-2 and other cytokines that stimulate the helper t-cells and cytotoxic t-cells to divide
  3. cytotoxic t-cells bind to other virus-infected cells
  4. each cytotoxic t-cell secretes proteases and perforin, which inserts into the plasma membrane of a virus-infected cell and forms channels. the cell takes up water and proteases and bursts
  5. the cytotoxic t-cell can then kill other virus-infected cells
47
Q

what are natural killer cells?

A

they destroy virus-infected and cancerous cells by secreting toxic chemicals
they recognise general features of virus-infected and cancerous cells as part of non-specific immunity
they can also be linked to target cells by antibodies

48
Q

a summary of innate and aquired immunity

A

primary immune response- initial exposure to an antigen, antigen production is slower and lower
secondary immune response- subsequent exposure to same antigen, faster and larger antibody production, memory b-cells qulickly stimulated to differentiate and multiply, immunological memory
active immunity- aquired response to exposure to antigen, natural or as a vaccination,
passive immunity- direct transfer of antibodies from one individual to another
immune tolerance - the body telling the difference between itself and non-self

BM108 🧬 (17 decks)

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