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FoM - normal function > foundations in immunology > Flashcards

foundations in immunology Flashcards

1
Q

what are the 3 layers behind the immune system?

A

external barrier
innate immunity
adaptive immunity

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2
Q

what are the external barriers?

A

the surface epithelial layers of the body, through which the pathogen must cross and penetrate to cause an infection.

It is made up of:

  1. Skin
  2. Mucus - Mucosal epithelial cells that coat cell surfaces
    e.g. (mouth, nose, gastrointestinal tract, urinary tract, eye)
  3. Epithelial cells of the nasal passages and bronchi have Cilia, that move dust and other particles upwards (Mucociliary Escalator) and outside the body through sneezing and coughing.
  4. Flushing action of saliva, tears, and urine.
  5. Sweat contains high [NaCl] which inhibits the growth of microorganisms
  6. Stomach contains digestive enzymes and low pH environment due to HCl which kills off most microorganisms
  7. Sweat, tears, and saliva contains lysozymes that destroy invading pathogens.
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3
Q

what is the innate immune response (non-specific)?

A

It doesn’t distinguish between different types of pathogens, only between human cells and pathogens

  • Fast and immediate response
  • It has no memory, meaning it will produce the same response in the next encounter.
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4
Q

what is innate immunity divided into?

A

Cellular and humoral

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5
Q

what is cellular innate immunity made up of?

A

made up of cells:

Phagocytes subdivided into (Neutrophils, Monocytes, Macrophages)

Eosinophils and Mast cells

Basophils

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6
Q

what is humoral innate immunity made up of?

A

proteins/peptides/antibodies swimming in the ECF:

Complement and Cytokines

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7
Q

what are phagocytes?

A

the cells of the innate immune system that track down, engulf and destroy bacteria, other pathogens as well as damaged or dead cells.

Neutrophils, Monocytes, Macrophages are all considered {{c1::Phagocytes}}

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8
Q

what are neutrophils?

A

the most abundant white blood cells at 8x106/ml (50-60%), they track down, engulf and destroy pathogens.

They contain granules that are filled with enzymes e.g. peroxidases, alkaline and acid phosphates.

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9
Q

what are monocytes?

A

they form 5% of white blood cells and they swim around in the bloodstream, they are the largest white blood cell, larger than neutrophils and can engulf larger pathogens or substances.

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10
Q

what are macrophages?

A

they are differentiated monocytes present in body tissue that break down pathogens and process their antigens then present it to the cells of the adapative immune system to produce a specific immune response in the form of Antibodies and Cytotoxic T cells.

When they present antigen they are called Antigen Presenting Cells (APCs)

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11
Q

what are the 7 stages of phagocytosis?

A
  1. movement of phagocyte toward the microbe
  2. attachment of microbes of phagocyte surface
  3. endocytosis of microbe
  4. formation of phagosome
  5. fusion of phagosome with lysosome
  6. killing of microbe through digestion by enzymes
  7. discharge of waste materials
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12
Q

what is the adaptive immune response?

A

Distinguishes between different pathogens based on the antigens on them.

  • Slow response
  • Develops immunological memory of the encounter with the pathogen
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13
Q

what are eosinophil?

A

they are white blood cells that help combat parasitic infections, they are involved in allergy and asthma, and have granules that contain enzymes.

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14
Q

what are mast cells?

A

they are a type of white blood cells that combat parasitic infections, they contain IgE receptors on their surfaces which are specific to IgE antibodies.

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15
Q

give an example of when IgE antibodies are produced:

A

against allergens e.g. pollen and foods

when allergens bind to IgE antibodies, Mast cells are activated and produce histamine which then causes an allergic response e.g. watery eyes and runny nose.

a large histamine release might cause: Contraction of respiratory ways, blood vessel dilation, itchiness, gastric secretion

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16
Q

what are basophils?

A

the least abundant white blood cells, less than 1%, they contain large cytoplasmic granules with inflammatory mediators.

maybes involved in parasitic infections

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17
Q

what are cytokines?

A

small proteins secreted by both immune and nonimmune cells in response to stimulus.

They communicate to other cells by binding to specific receptors producing signalling molecules that make an intracellular response causing a biological effect.

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18
Q

what are the 4 functions of cytokines in innate and adaptive/acquired immunity?

A
  1. Differentiation - helps stem cell development
  2. Activation - activation of phagocytes
  3. Chemotaxis - recruiting more immune cells to enhance the response and recovery
  4. Enhancing cytotoxicity - enhances the role of cytotoxic T cells
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19
Q

what happens to T and B lymphocytes in the bone marrow?

A

The production stage takes place but they are immature in that stage, they haven’t acquired the ability to recognize and interact with pathogens.

20
Q

what happens in the maturation stage of T and B lymphocyte development?

A

they acquire structures that allow them to recognize and interact with pathogens by antigens

Maturation of B lymphocyte cells occurs in the Bone marrow

Maturation of T lymphocyte cells occurs in the Thymus which is divided into cortex and medulla and is located in the anterior mediastinum.

21
Q

what do naive T and B lymphocytes gain when they mature?

A

T lymphocytes gain T Cell Receptors (TCR)

B Lymphocytes gain B Cell Receptors (BCR)

22
Q

when does the lymphocyte activation stage occur?

A

when they react with pathogens to induce an immune response specific to a certain pathogen,

occurs in Secondary Lymphatic Organs e.g. Lymph Nodes, spleen, mucosal immune system (peyer’s patches), tonsils

23
Q

what is the lymphatic system composed of?

A

The lymphatic vessels

Primary lymphatic organs (Bone Marrow & Thymus)

Secondary lymphatic organs (Lymph nodes & Spleen)

24
Q

what are the 3 functions of the lymphatic system?

A
  1. Drainage of tissue - collects excess fluid and returns it to the bloodstream.
  2. Absorption and transport of fatty acids and fats.
  3. Immunity - transports pathogens and antigens to lymphoid organs where they interact with lymphocytes to induce a response.
24
Q

what are lymph nodes?

A

they are encapsulated, secondary lymphatic organs, numbered at about 500 throughout the body.

They have access to antigens encountered in most tissues and their main function is inducing adaptive immune responses to antigens.

25
Q

what is haematopoiesis?

A

the process where blood cells are produced in the bone marrow from hematopoietic stem cells

26
Q

what is the spleen?

A

it’s a secondary lymphoid organ, that weighs 150g, located in the left upper quadrant of the abdomen, and made up of two parts:

The red pulp is a blood filter that removes ageing, damaged blood cells, and particles.

The white pulp mainly contains lymphocytes and initiates immune responses against blood-borne antigens.

27
Q

what do T cells do?

A

they are responsible for cell-mediated immunity of the adaptive immunity system and assisting B cells, there are about 10^12 of them in the human body.

28
Q

what are the 2 types of T cells?

A

Cytotoxic T cells (CD8+)
They contain CD8+ receptors

They have T-cell receptor (TCR) on the surface through which they recognize antigens only when bound to MHC I.

Their main role is to kill pathogens or infected cells.

Helper T cells (CD4+)
They contain CD4+ receptors

They have T-cell receptor (TCR) on the surface through which they recognize antigens only when bound to MHC II.

Their main role is to stimulate B cells to produce antibodies

29
Q

what are the 2 products that are secreted to allow foreign bodies and infected cells to be killed?

A

Perforins - form holes through the membrane of the target cell.

Granzymes - enzymes that promote apoptosis in the target cell.

30
Q

what are the 4 types of effector CD4 T cells that target certain cells?

A

Th1 → Macrophages

Th2 → Eosinophils

Th17 → Neutrophils

Tfh → B cells

31
Q

What are the purposes of MHC Class I and MHC Class II proteins?

A

MHC Class I proteins are found on virtually all nucleated cells

They present ‘endogenously produced’ antigens/peptides i.e. inside cells, to CD8+ T cells and trigger a cytotoxic response.

32
Q

what are B cells?

A

they are cells involved in Humoral Immunity, which mainly produce antibodies that are directed against specific antigens.

They are produced and mature in the Bone marrow (Primary Lymphatic Organ)

They express B-cell receptors (BCR) on their surfaces, where antigens bind.

33
Q

What are the purposes of MHC Class II proteins?

A

MHC Class II proteins are only found on Antigen Presenting Cells (APCs) like macrophages

They present ‘exogenously produced’ antigens/peptides, i.e. outside cells, to CD4+ T cells

34
Q

what 2 cells are B cells differentiated when activated?

A

Plasma Cells - short-lived cells that are responsible for antibody (Ab) production.

Memory B Cells remember the pathogen for faster antibody production in the next encounter.

35
Q

what is an epitope?

A

the part of an antigen to which an antigen receptor or an antibody attaches.

If B cells recognize two epitopes through their antigen receptors they produce two types of antibodies, each specific for an epitope.

36
Q

what 2 regions are antibodies divided into?

A

Antigen Binding Region (Fab), where it interacts with the antigen. (upper region)

Fc Region (lower region)

36
Q

what is antigens?

A

they are substances that cause an immune response by identifying substances in or markers on cells.

e.g. they can be cell membranes, or surface proteins, or exotoxins of bacteria.

37
Q

what are antibodies?

A

they are proteins that are produced as an immune response against antigens by B cells.

Different antigens lead to the production of different antibodies.

38
Q

what are the 5 Different classes of Immunoglobulins (Ig) / Antibodies (GAMED)?

A

IgG - Produced later in the infection → (can cross the placenta)

IgA - Protect mucosal surfaces, resistant to stomach acid.

IgM - 1st Class to be produced in the infection.

IgE - Defend against parasites, causes allergies

IgD - No known function, it is the B cell receptor.

38
Q

what is the complement system?

A

it consists of more than 30 proteins/factors that are found in the plasma in an inactive form.

They are activated in a cascade-like format, which takes place on the surface of the target cells.

38
Q

what is the final result of the activation of the complement system in any of the pathways?

A

the production of a Membrane Attack Complex (MAC), which leads to the lysis of the target cell.

39
Q

what are the 3 pathways that activate the complement system?

A

Alternative Pathway (Effector mechanism of the Innate immune system)

Classical Pathway (Effector mechanism of the Adaptive immune system)

Lectin Pathway (Effector mechanism of the Innate immune system)

39
Q

what are the 3 functions of antibodies?

A

Neutralization - prevention of attachment and entry by surrounding pathogens/antigens

IgA antibody neutralises in the respiratory and gastrointestinal tract (mucous surfaces)

Opsonization - stimulation and facilitation of phagocytosis.

Complement activation through Classical Pathway - a component of the innate immunity which leads to direct-lysis of microbes.

40
Q

What are the 3 functions of the complement system?

A

Direct lysis of target cells through the Membrane Attack Complex (MAC)

Makes products that:
- Increase blood flow and act as chemo-attractants to recruit other immune cells to enhance the immune response (inflammation)

Opsonization - which is the facilitation and stimulation of phagocytosis

41
Q

what is active immunity?

A

immunity is acquired through the host’s own active response to a pathogen.

Presence of B memory cells

Long-Term & Takes weeks to form

42
Q

what is passive immunity?

A

immunity is acquired through the transfer of antibodies or lymphocytes specific to a microbe from another individual.

Absence of B memory cells

Short-term & Immediate

FoM - normal function (20 decks)

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