Lec 1 - Basic Immunology

Question 1

Compare the Innate and Adaptive Immune System

Answer 1

Innate; broad specificity, not affected by prior contact (do not get an enhanced response if already come into contact with pathogen), quick response for initial infection
Adaptive; v specific, affected by prior contact, long response time

Both primarily involve leukocytes and soluble factors

Question 2

give 4 examples of large surfaces that act as barriers to infections

Answer 2

• keratinised skin (v rare for bacteria to directly infect the skin, infection occurs once skin has been breached eg burn, wound)
• gastrointestinal and respiratory tract (both v large mucosal surfaces - susceptible to infections)
• urogenital tract (close contact between individuals required for transmission)

Question 3

give 2 examples of physical barriers

Answer 3

• tight junctions between epithelial cells that line the mucosal layer
• cilia that physically move mucus and any pathogens contained w/in mucus

Question 4

give 3 examples of chemicals that stop infection

Answer 4

• fatty acids (low pH) on the skin
• lysozyme secreted onto mucosal surfaces
• low pH enzymes eg pepsin

Question 5

how does the microbiome help prevent infection?

Answer 5

growth of commensals in the gut etc prevent the growth of pathogenic bacteria

Question 6

Where are leukocytes derived from and give the 2 main lineages that come from them?

Answer 6

pluripotent stem cells from bone marrow

create myeloid cells (macrophages, neutrophils) and lymphoid cells (TH cells, B cells, NK cells)

Question 7

Name the 2 types of phagocytes that exist

Answer 7

mononuclear phagocytes

neutrophils

Question 8

Describe neutrophils

Answer 8

• exist in the blood
• short lived (unless infection established)
• fast moving
• lysosomes secrete enzymes eg H2O2

Question 9

Describe the 2 locations where mononuclear phagocytes exist and describe them

Answer 9

• in blood = monocytes
• in tissues = macrophages
• live for a long time (months-years)
• can stimulate the adaptive immune response

Question 10

Where are mast cells found?

Answer 10

• tissues (like MAcrophages) underlying the mucosal layer

Question 11

What are NK cells effective against and how do they work?

Answer 11

• effective against intracellular viruses

- release their granules and induce apoptosis

Question 12

Name the 3 types of soluble proteins that exist

Answer 12

defensins, interferons, complement

Question 13

Describe defensins

Answer 13

• small, +vely charged peptides that can insert themselves into and disrupt bacterial membranes

Question 14

What types of cells produce interferons?

Answer 14

any cell that has been infected with a virus

Question 15

give the 3 results following IFNa/b release

Answer 15

• signals nearby cells to resist virus replication
• signals NK cells to kill infected
• increase in MHC-I receptors and antigen presentation to stimulate adaptive response

Question 16

What is the name of the MAIN component of the complement system and give the name of the structures that form when it is cleaved?

Answer 16

C3

cleaved into C3a and C3b

Question 17

Describe the 3 pathways that can lead to complement activation

Answer 17

• MB Lectin pathway (lectins bind to mannose sugars on surface of bacteria)
• antigen:antibody complexes
• pathogen surfaces eg LPS

Question 18

Describe the 3 outcomes of complements activation

Answer 18

• opsonisation (C3b coat pathogens and phagocytes with C3b receptors are recruited and phagocytosis)
• recruits other members of immune system (chemoattractants eg C5a released, recruit neutrophils and anaphylatoxins, C3a, stimulate mast cells to promote inflammation)
• cell lysis (C9 forms polymers, hollow tubes forming membrane attack complex)

Question 19

Describe what occurs in the LOCAL (inflammation) and SYSTEMIC (fever) responses.

Answer 19

Local;
increase in bloody flow to capillaries, dilation of capillaries, increase in permeability
ALL allow neutrophils and interferons etc to escape into tissues (site of infection)

Systemic;
acts on hypothalamus to increase body temp in effort to kill bacteria