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Responding to antigens Flashcards

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1
Q

Innate immune response

A

An inborn system that lacks specificity and memory
Stimulates - inflammation and phagocytosis → both can occur quickly, even if the host has never been previously exposed to a particular pathogen.

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2
Q

Inflammatory response

A

Reaction to an infection, injury, damaged tissue- results in:
Heat - due to increased blood flow
Pain - due to systemic response (ie fever), the stimulation of nerve endings through the release of histamine and swelling putting pressure on pain receptors.
Swelling - due to movement of fluid into tissues after vasodilation
Redness - due to vasodilation of blood vessels, leading to red blood cells released into tissue.
Due to accumulation of fluids and proteins and an increased blood supply to the infected region.

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3
Q

Stages of inflammatory response

A
  1. Initiation - involves the release of cytokines from damaged cells which trigger mast cells to undergo degranulation (release histamine)
  2. Vasodilation - Histamine from mast cells promotes vasodilation and blood vessel permeability allowing neutrophils and other immune cells travel to the site of infection (also stimulated by cytokines)
  3. Migration - phagocytes and complement proteins travel around the body and move from the permeable vessel to the infected site. They remove indigestible material.
    → Resolution includes a reversal of all the processes that produced the acute inflammation
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4
Q

Monocytes

A
  • found in tissue
  • Undergo differentiation into macrophages or dendritic cell
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5
Q

Neutrophils

A
  • found in blood
  • Most abundant circulating white blood cells
  • Usually the first to site of infection
  • Undergo phagocytosis
  • Short life span
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6
Q

Dendritic cells

A
  • found in tissue
  • Antigen presenting cells
  • Undergo phagocytosis (presenting their antigens to T cells to activate the adaptive immune response)
  • Have branched projections, providing them with a large SA:V improving their phagocytic and antigen presenting properties.
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7
Q

Eosinophils

A
  • found in blood
  • Defend against larger parasitic agents (too large to be attacked by phagocytosis)
  • Undergo degranulation (release of histamines)
  • Undergo phagocytosis
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8
Q

Natural killer cells

A
  • Found in blood
  • Once pathogens have gained entry into the body cells and become intracellular, they cannot be directly attacked by innate immune cells → are eliminated by NK cells
  • Eliminate virus, infected cells and cancer cells by degranulation and induce apoptosis
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9
Q

Mast cells

A
  • found in tissue
  • Mediate inflammatory response
  • Upon stimulation, they release histamines, cytokines and heparin through degranulation
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10
Q

Macrophages

A
  • found in tissue
  • Undergo phagocytosis
  • Initiate acute inflammatory responses through secretion of various cytokines
  • Antigen-presenting cells
  • Recruit other immune cells to an infection site
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11
Q

Degranulation

A

Process where immune cells release various toxic chemicals stored within secretory vesicles (cytoplasmic granules)
Natural killer cell degradation - releases proteases and perforin proteins, which insert holes in plasma membrane of foreign cells and induce apoptosis (programmed cell death)

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12
Q

Phagocytosis

A
  1. The pathogen is identified by a pattern recognition receptor (PRR)
  2. Engulfment - ATP required to carry out endocytosis
  3. Digestion - pathogen is engulfed in a vesicle called a phagosome. This fuses with a lysosome (forming a phagolysosome) and digestion of pathogen occurs using lysosomes
  4. Secretion - undigested material is secreted using exocytosis
  5. In macrophages and dendritic cells, some of this material is presented on MHC-II markers to activate the adaptive immune system
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13
Q

Cytokines

A

Cytokines are a broad group of molecules which facilitate communication between immune cells and attracts other immune cells to help destroy the pathogen

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14
Q

Histamine

A

Histamine is a type of cytokine that increases vascular permeability of blood vessels in inflamed areas making it easier for neutrophils, macrophages and blood proteins to squeeze out and into infected tissue

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15
Q

Complement proteins

A

Complement = proteins that are dissolved in the plasma of one’s blood - they complement or add to the function of immune cells.
1. Process of chemotaxis which attracting phagocytes to the area (for inflammatory response)
2. They opsonization pathogens, marking them for destruction by phagocytes (specific proteins will attach to bacterias and mark for destruction)
3. They destroy pathogens by lysis (causing the bacterial cell membrane to rupture) through the initiation of the membrane-attack complex (MAC) (punches holes in bacteria and lets fluid inside the cytoplasm of bacteria out and kills it)

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16
Q

Interferons

A

Increase the resistance of of uninfected cells to viral cells
When a cell is infected by a virus, the virus enters the cell and produces viral material. This signals the host cell to produce interferons, signalling molecules (cytokines). The virus infected cell will secrete interferons which attach to receptors on nearby cells and act as a warning signal so the cell can prepare for possible virus infection. The virus in the cell will replicate and when the host cell dies, the viral particles will be released

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17
Q

Fever → second line defence

A

Following a cascade of events which results in a higher body temp to conserve heat, microbe reproduction in the body is slowed

18
Q

Physical barriers

A

Innate barriers that prevent the entry of pathogens into the body/ plant

19
Q

Blood clotting → part of second line of defence

A
  • Platelets can ‘plug’ a wound area, producing serotonin to trigger blood vessels to constrict, minimising blood loss.
  • Also produce thromboplastin to trigger a cascade of events to form a permanent clot.
  • A protein chemical called FIBRIN is the key product made.
20
Q

Antigen

A

Any substance that triggers an immune response through the production of antibodies or immunoglobulins
Can be bacteria, virus, pollen, grains, chemicals, drugs, venom etc
- Self-antigens - antigens on cells are recognised by self-receptors as being part of the same body
Not foreign, usually tolerated by the immune system
- Non-self antigens - antigens that do not belong to the body’s own cells
Can be identified as invaders and can be attacked by the immune system.

21
Q

Antigen recognition depends on MHC markers

A

MHC-I is present on all nucleated cells of the body. Contains the binding site for an antigen. This allows cells to be recognised as ‘self’ so they will not be attacked by natural killer cells or cytotoxic T cells.
MHC-II is presented on specific WBC, including APC (macrophages and dendritic cells) and helper T cells.

22
Q

Pathogen

A

A pathogen is a causative biological agent of disease or illness to its host. Can be cellular or non-cellular

23
Q

Allergic response

A
  1. Sensation involves the body’s first encounter with the allergen. The allergen binds with complimentary B cell antibody receptor
  2. This initiates a cascade of events that turn B cells into plasma cells that secrete a very high level of IgE antibody, coating the surface of mast cells. No immune response is activated. → sensitisation stage
  3. Re-exposure involves the allergen binding with complementarity IgE receptors on the mast cells, triggering degranulation and histamine secretion. This causes heightened inflammation (involve pain, heat, swelling)
24
Q

Cellular pathogen

A

Classified as living organisms → made up of cells that can reproduce independently without relying on the host machinery.
Bacteria, protozoan, fungi, parasites, arthropods

25
Q

Bacteria

A
  • Prokaryotic cells, no membrane bound nucleus or organelles, contains 1 circular chromosome
  • Under favourable conditions, enormous numbers can be produced through binary fission (main issue with bacteria- fast rate of multiplying)
  • Exotoxins - releases defence chemical
  • Endotoxins- released when cell goes through lysis
26
Q

Protozoan

A
  • Eukaryotes that posses a membrane bound nucleus
  • Infections caused by protozoa can spread by sexual transmission, or insect vector eg. malaria
  • Are able to multiply in humans, can survive in human host while causing disease
27
Q

Fungi

A
  • Eukaryotic organisms
  • Secrete digestive enzymes and other chemicals that can cause disease on host
28
Q

Parasites

A
  • Multicellular eukaryotes
  • Disease causing organisms
29
Q

Arthropods

A

Multicellular animals that acts as major vectors of disease in plants / animals

30
Q

Non cellular pathogen

A

Non- living organisms (no metabolic activity) Not made up of cells and are unable to reproduce without a host (hijack the hosts processes in order to replicate)
No membrane or cytosol, just molecular
- Virus, viroids, prions

31
Q

Virus

A
  • Non cellular agents consisting of DNA or RNA enclosed within a protein shell (capsid)
  • Contain enzymes necessary for the reproduction of the virus - reproduce by inserting their nucleic acid into host cell, host cell uses it to make new viruses
32
Q

Viroids

A
  • Piece of RNA/DNA not enclosed by boundary
  • Usually only infect plants
33
Q

Prions

A
  • Abnormally folded tertiary structure
  • Fatal degenerative disease of NS / ‘mad cow disease’
  • No genetic material
34
Q

Physical barriers animal

A

Intact skin:
The epidermis of the skin is composed of many layers of cells (keratinocytes) with the outermost layer consisting of dead cells. The constant shedding of these dead surface cells is an effective barrier against entry of pathogens.

Mucous membranes:
line inner spaces of the airways, gut, urogenital tract, consist of epithelial cells.
The mucus membranes secrete a thick gelatinous fluid - mucus that can trap particulate matter, including pathogens.
Airways include many cells with cilia on outer surfaces, regular beating of cilia moves mucus from deep in airways to back of throat, the mucus that is swallowed will be destroyed by acid in the stomach

Ear wax:
Reduces the access pathogens have to the eardrum and canal, also protects the ear from dust, foreign particles

35
Q

Physical barriers for plants
C TB S CW L T
cat to be saw cows walking left today

A
  • Cuticle: Waxy covering on leaves that reduces water accumulation + helps prevent cells becoming infected
  • Thick bark: external layer that acts similar to intact skin
  • Stomata: can be closed to prevent pathogens entering; also may sit lower down, to protect the plant.
  • Cell wall: cellulose wall can protect cells from infection from viruses
  • Leaf orientation: vertical leaves make it harder for pathogens to attack as water is unable to accumulate on the leaf surface.
  • Thorns and spikes: modified leaves/ branches which protect the plants from grazing animals.
36
Q

Chemical barriers

A

Innate barriers that use enzymes to kill pathogens and prevent invasion into a host

37
Q

Chemical barriers for animals

A

Destroy pathogens on the outer body surface, at body openings, on inner body linings
- Lysozyme: (enzyme in body secretions - sweat, mucus, tear, saliva) helps in first line defence that kills pathogens.
- Sebum: provides a protective and anti- microbial film on skin.
- Stomach acid digestive enzymes: kill pathogens that enter the digestive tract in food and water.

38
Q

Chemical barriers for plants

A

Produce antimicrobial chemicals, antimicrobial proteins and antimicrobial enzymes that prevent pathogens from entering the plant/ affect pathogen functioning
- Tannins: a bitter tasting substance that may deter predators
- Saponin: plant proteins that disrupt bacterial and fungal cell membranes

39
Q

Microbiota barriers for animals

A

‘Normal flora’: refers to the non pathogenic bacteria that are the normal residents in particular region of the body (gut, mouth, throat, genital tract)
Their presence inhibits the growth of pathogenic microbes
Eg. vaginaproduces lactic acid which prevents the establishment of pathogenic microbes.

40
Q

Microbiota barriers for plants

A

‘Normal flora’: prevents colonisation or growth of pathogen

Biology (15 decks)

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