Innate immunity

Question 1

Immunological barriers in the body

Answer 1

Tight epithelial cells:
Present in skin, eyes, nose, lungs and the gut.

Lysosomes:
Present in the eyes and nose

Pepsin and low pH in the gut

Fatty acids in the skin

Antibiotic peptides:
Present in the skin, gut, and lungs

Mucus and cilia in the lungs

Microbiological flora in the skin and gut that outcompete pathogenic bacteria.

Question 2

Functions of the innate immune system

Answer 2

Prevents infection

Stimulate acute inflammation

Provides a rapid response to infection

Question 3

Pattern recognition receptors (PPRs)

Answer 3

Receptors on the cells on the immune innate system that recognise molecules typical of pathogens.

These receptors are germline and non specific

Question 4

Pathogen associated molecular patterns (PAMPs)

Answer 4

Present typical on the surface of pathogens and are recognised by the pattern recognition receptors of innate immune cells.

Allows immune cells to differentiate between self and non-self cells.

PAMPs include:
glycans
glycoconjugates
lipopolysaccharides 
endotoxins

Question 5

Toll like receptors

Answer 5

A type of pattern recognition receptors that recognises many PAMPs like lipopolysaccharide.

Question 6

Mannonse binding ligand

Answer 6

A type of pattern recognition receptor in innate immune cells that recognises a specific spacing of mannose and fucose residues from the glycans of bacteria.

This works by the ligand having high affinity to the mannose and fucose residue in lower organisms

Question 7

Complement

Answer 7

Soluble mediators composed of a series of enzymes produced in the liver that is triggered by an infection.

Enzymes are released in the blood. Activation of one enzyme activates even more enzymes in a ‘triggered enzyme cascade’.

Can be activated by three methods:
Classical- from an antibody-antigen complex
Alternative- from a bacteria
By a mannan-binding lectin

Includes:
Terminal pathway
Opsonisation

Question 8

Soluble mediators

Answer 8

Substances secreted by phagocytes that circulate in tissues and the blood. They mediate effects that affect infection.

Includes:
Cytokines- TNF-alpha, IL
Chemokines: CXCL8
Interferons
Complements

Question 9

Terminal pathway

Answer 9

Cells of the innate immune system form transmembrane proteins which punctures the cell membranes of bacteria/ other pathogens.

This causes the cell to lysis and die.

Part of the complement system.

Question 10

Oponisation

Answer 10

Occurs when a pathogen is tagged by the immune system, which facilitates the phagocytosis of the pathogen.

The activated complement C3b sticks to the pathogen .

C3b then binds to receptors on the macrophage and neutrophils which phagocytose the bacteria.

Question 11

Alpha interferon

Answer 11

A soluble mediator secreted by innate immune cells.

This interferon binds to a plasma membrane receptor and activates JAK-STAT intracellular signalling.

This affects transcription of genes and promotes the production of antiviral proteins and inhibits the synthesis of viral proteins.

This helps to prevent the proliferation of viral cells.

Question 12

Connections between innate and adaptive immunity

Answer 12

Inflammation caused by innate immunity attracts T and B lymphocytes to lymph nodes for activation.

Antibodies act on innate immunity to perform an action:
Opsonisation and phagocytosis
Mast cells
Complement

Innate immunity directly activates T cells

Question 13

Defence mechanisms in the skin

Answer 13

Lactic acid and fatty acid secreted from sweat and sebaceous glands are toxic for many bacteria.

Question 14

Roll of mucous membrane in immune defence

Answer 14

Mucous membrane in the lining traps bacteria and prevents them from adhering to epithelial cells.

Bacteria can be removed by cilia brushing it away and the body actively removing it by coughing, sneezing or swallowing.

Question 15

Examples of microbacterial factors in bodily fluids

Answer 15

Acid in gastric juice, provides low pH for destroying bacteria.

Spermine and zinc in semen

Lactoperoxidase in milk

Lysosomes in tears, nasal secretions and saliva

Question 16

Microbial antagonism as an example of an immune defence.

Answer 16

1. Commensal organisms in the natural flora of the body compete with pathogenic organisms for nutrients.
2. The commensals have a physical advantage since they previously occupied the space.
3. The commensals also produce substances to inhibit pathogenic growth like acid or colicins.

Question 17

Natural killer cells

Answer 17

Larger granular lymphocytes which recognised recognised virus-infected cells.

Causes NK cells to be activated and kills infected cells by forming transmembrane pores.