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Organ System Anatomy, Physiology and Pathology - BPT06 > Immune System Physiology > Flashcards

Immune System Physiology Flashcards

1
Q

Immune System - Function

A

Protects organisms from pathogenic agents and removes damaged component of the organism itself.
Complex collection of cells and organs that destroy or neutralize pathogens.

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2
Q

Types of Pathogens

A 
Microorganisms that cause a specific disease.
Virus
Bacteria 
Fungi
Parasites
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3
Q

Virus

A

Smallest, very specific. Either RNA or DNA.
Not living, cannot reproduce on their own (need a host).
Intracellular - has to enter the cell to reproduce (with cell’s metabolic machinery).
Infected cell lyses, releasing the virus to invade others.

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4
Q

Bacteria

A

Prokaryotic cells, generally harmless but some can cause infectious diseases.
Unicellular. Extracellular pathogen (grow in extracellular fluid). Reproduce on their own.
Gets eaten (phagocytosis).
Can release toxins, cause fever.

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5
Q

Fungi

A

Less common. Single or multi-cellular eukaryotic organism.
Mycoses: fungal infection in animals.
Causes infection such as athlete’s foot and ringworm.

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6
Q

Parasites

A

Less common. Invade host to obtain nutrients and harm it.
Protozoans: unicellular eukaryotic organisms.
Metazoans: multicellular animals.
Spread through vector or fecal-oral route.

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7
Q

Immune System - Composition

A
  1. Physical barriers: they prevent at all time pathogenic invasion into the body tissues.
  2. Lymphoid tissues: sites where leukocytes develop, reside and encounter foreign materials.
  3. Leukocytes or white blood cells.
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8
Q

Physical Barrier

A 
• Non-specific defense
• Prevent entry of pathogens
• Hostile chemical environment (acidic pH discourages bacteria growth)
Ciliated mucosa - Airway
GI tract mucosa
Skin
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9
Q

Lymphatic System - Functions

A
  • Drain body fluids and return them to the bloodstream.
  • Transport of dietary lipids and fat-soluble vitamins absorbed in the gut.
  • Transportation and housing of the immune cells.
  • Development of immune cells and of the immune response. (defense against pathogens)
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10
Q

Lymphatic System Circulation

A

Open system.
Capillaries leak → accumulation of interstitial fluid → interstitial pressure increases → spaces between cells open up → fluid enters lymphatic capillaries → becomes lymph → travels through lymph nodes → empty into larger lymphatic vessels.

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11
Q

Lymphatic Vessels

A
  • Lymphatic trunks
  • Lymphatic ducts
  • Subclavian veins
    Lymphatic capillaries empty into them.
    Similar to veins, have valves.
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12
Q

Lymph Node - where?

A

Filter for lymph, where fluid can be exposed to immune cells.
Found near groin, armpit, neck, chest, and abdomen.

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13
Q

Central Lymphoid Tissue

A

Sites of leukocyte production and maturation:

  • Bone marrow: all leukocytes developed here. B-cells
  • Thymus: maturation site for T lymphocytes.
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14
Q

Peripheral Lymphoid Tissue

A

Where leukocytes contact pathogens and become activated.

  • Lymph nodes: sites of adaptive immune responses & filters of lymph.
  • Spleen: removes blood born pathogens.
  • Lymphoid nodules: dense cluster of lymphocytes in areas routinely exposed to pathogens.
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15
Q

The 5 Types of Leukocytes

A 
Granulocytes: 
- Neutrophil
- Eosinophil
- Basophil
Lack granules:
- Monocytes
- Lymphocytes
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16
Q

Which immune cells are found in the tissue?

A

Macrophages, mast cells and dendritic cells.

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17
Q

Phagocytes

A

Neutrophils, eosinophils, monocytes, macrophage and dendritic cells.
Phagocytosis: removes extracellular pathogens and cell debris.

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18
Q

Lymphocytes

A

Provide immune system with diversity, specificity and memory!

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19
Q

Two Types of Immune Response

A

Innate immune response: relatively rapid but non-specific.

Adaptive immune response: slower, but highly specific.

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20
Q

Innate Immune Response - Function

A
  • Prevent entry of pathogens
  • Limit the spread of infection
  • Eliminate pathogen (sometimes)
  • Mediate start of adaptive immunity
  • Contribute to the clearance of pathogen (phagocytosis always innate immunity)
    Keep infection in check until adaptive immunity arrives.
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21
Q

Components of Innate Immunity

A
  • Physical barriers
  • Phagocytes
  • Soluble mediators
  • Natural killer cells
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22
Q

Cells of the Innate Immune System - Monocytes

A

Large mononuclear cells. 5-7% of WBC.
Differentiate into macrophages in tissue.
Phagocytic cells that act as a scavenger, can trigger inflammation.

23
Q

Cells of the Innate Immune System - Dendritic Cells

A

Link between innate and adaptive immunity.
Antigen presenting cells. Call for help from t-cells.
Phagocytic cells.

24
Q

Cells of the Innate Immune System - Neutrophils

A

Granulocytes → multilobed nuclei.
60% of WBC.
Phagocytic, extremely effective in killing bacteria.

25
Q

Cells of the Innate Immune System - Eosinophils

A

0-5% of WBC.

Parasitic infections → release of granules kills pathogens too big to be eliminated by phagocytosis.

26
Q

Cells of the Innate Immune System - Basophils and Mast cells

A

Involved in allergic reaction.

Contain granules with histamine and other inflammatory mediators.

27
Q

Cells of the Innate Immune System - Natural Killer Cells

A

Lymphocytes that induce apoptosis in cells infected with intracellular pathogens, such as viruses or cancer
cells.

28
Q

Soluble Mediators - Interferons

A

proteins involved in The Shut down and intense reduction of initiation translation, preventing virus production.

29
Q

Soluble Mediators - Complement System

A

Composed of 30 plasma proteins that contribute to removal of pathogens (especially bacteria)
Activated in 3 ways:
- Formation of membrane attack complex (MAC).
- Opsonisation: Help phagocytes recognize pathogens.
- Increase inflammatory response.

30
Q

Adaptive Immune Response

A
  • Specificity: antigens are recognized by B and T cells. An infinite number of receptors to specifically
    recognize every pathogen.
  • Immunological memory: protects the body from
    getting diseases repeatedly from the same pathogen.
  • Self-recognition: capable of distinguish between self-antigens and foreign antigens.
31
Q

What are the primary cells that control the adaptive immune response?

A

Lymphocytes, T cells and B cells (produce antibodies).

32
Q

T - Cells Regions

A

Regulate B-cell activity. T-cells recognize antigens though t-cell receptors.
Constant region: similar among T-cells.
Variable region: assume extremely different and specific AA sequences, enabling recognition of multitude of antigens.

33
Q

T - Cell Chains

A

Two chains.
Antigen-binding site: terminal end of both chains.
Each T-cell produces one type of receptor - specific for a single antigen or portion of antigen (epitope).

34
Q

Pathogen Recognition by T - Cell

A

Do not recognize pathogens on their own.
The antigen needs to be processed and presented attached to specific protein: major histocompatibility
complex (MHC) molecule.

35
Q

Major Histocompatibility Complex - Class I

A 
Antigens derived from intracellular pathogens (viruses) are presented through MHC class I. Viruses infect nearly every tissue → almost all cells express MCH I.
Cytotoxic T cells bind to MCH I.
36
Q

Cytotoxic T Cells

A

Bind to class I MHC. Kill cells presenting those antigens by inducing apoptosis.

37
Q

Major Histocompatibility Complex - Class II

A

Antigens derived from extracellular pathogens (bacteria, fungi) are presented through MHC class II.
Expressed by antigen-presenting cells - dendritic cells (eat it, chop it, show it to T cells in lymph nodes).
Helper T cells (Th) bind to MCH II.

38
Q

Helper T Cells

A

Bind to MHC II, recognize antigens from extracellular pathogens.
Secrete cytokines (enhance other immune responses)
Th1 helps macrophages produce inflammatory response
Th2 help B cells produce antibodies.

39
Q

B Cell

A

Can recognize native, unprocessed antigen, do not require participation of MHC and antigen-presenting cells.
B cell receptor are membrane bound antibodies.

40
Q

Antibody

A

Recognize antigen on pathogen and bind to it. Phagocytes recognize antibody and perform phagocytosis.
Y -shaped. 4 protein chains: 2 identical heavy, 2 identical light.
Variable region (infinite), constant region (5).

41
Q

Antigen

A

Protein (98% of the time) on pathogens that can be recognized by our immune system. Trigger immune response.

42
Q

B Cell Proliferation

A

Stimulated when B cell binds to antigen.

Become either memory B cell or antibody synthesizing plasma cell.

43
Q

Inactivation or Disposal of Antigen

A
  • Neutralization: the antibody blocks an antigen’s activity just by binding to it.
  • Agglutination: antigens are clumped together simultaneously by thousands of antibodies
  • Opsonization: once bound to antibodies, an antigen is more susceptible to phagocytosis.
  • Activation of NK cells: antibodies can mark cells or death by the killing action of NK cells
44
Q

Generation of Diversity - Light Chain

A

Single exon codes for constant region.
Variable region coded by 2 exons Vk and Jk:
40 V genes joined to one of its 5 J genes.
Thousands of possible outcomes.

45
Q

Generation of Diversity - Heavy Chain

A

Heavy chain is coded by 3 exons:

65 VH - 27 DH - 6JH → millions of possible outcomes.

46
Q

How can there be infinite variables of receptors?

A

Thousands of possible outcomes for the light chain +
Millions of possible outcomes for the heavy chain.
In theory any heavy chain can be produced together with any light chain in a single B cell => 3.5 × 10(í 6. veldi) different antibody specificities.

47
Q

Generation of Diversity - Somatic Mutation

A

Additional mutation during B-cell reproduction (successfully bound to antigen).

48
Q

Generation of Diversity - Affinity Maturation

A

Mutated B cells that bind better will outcompete poorer binders.

49
Q

Lymphocyte Development - Self Tolerance

A

Lymphocytes can be generated with specificity for any antigen, including self-antigens → dangerous, must be prevented from reacting → self tolarance.

50
Q

Central Tolerance

A

Immature B cell recognizes self antigen → apoptosis or anergy.

51
Q

T-Lymphocyte Development - Positive Selection

A 
Only thymocytes able to bind self-MHC survive
Recognition of MCH class I => CD8+ (Cytotoxic T cell)
Recognition of MCH class II=> CD4+ (T helper cell)
52
Q

T-Lymphocyte Development - Negative Selection

A

Dendritic cells present self-antigens to thymocytes.

Thymocytes that recognize self-antigens undergo apoptosis.

53
Q

Loss of Self-Tolerance

A

The failure to inactivate or eliminate self-reactive cells leads to autoimmunity.
Immune system will attack our own tissue.

Organ System Anatomy, Physiology and Pathology - BPT06 (34 decks)

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