introduction to immunology

Question 1

how do we know that we have an immune system?

Answer 1

body reacts to foreign substances
- cuts/scrapes, redness, swelling, secretions, etc.

infection protects us from repeated infections

vaccines work

our body can immunologically reject organ transplants and blood transfusions

Question 2

what’s a hypersensitivity reaction?

Answer 2

extreme or unnecessary immune response that the body has to an antigen

Question 3

how does inflammation appear on the skin/externally?

Answer 3

redness and swelling

Question 4

what is meant by “infection protects us from repeated infection”?

Answer 4

in subsequence infection (or exposure event to the same antigen), we get a faster and larger immune response due to immunological memory, a part of the adaptive immune response

note: there’s no improvement in the innate response

Question 5

describe the relationship between antigens and antibodies

Answer 5

ANTIbody GENerator

antibodies are produced by B cells in response to antigens and used to mark antigens for destruction

antigens are foreign substances

Question 6

why do vaccines work?

Answer 6

due to the adaptive immune response and immunological memory

Question 7

what did E. Donnall Thomas win the nobel prize for in regards to immunology? describe his findings

Answer 7

for his study on bone marrow transplants and immunological rejections – he conducted the first match bone marrow transplant in humans

FINDINGS: if subjects were…

immunologically mismatched, transplants were immunologically rejected = death

immunologically matched = transplants were tolerated for a few days before patient’s health declines

immunologically matched and treated with methotrexate (which wipes out recipient’s immune system) patient experienced better results and was unable to immunologically reject the transplant

Question 8

how do we know that we need an immune response?

Answer 8

severe combined immune deficiency in children is lethal without treatment

immune deficient model organisms are unable to prevent infection
- experiment with a fly where they had their toll-like receptors removed (TLRs), an essential part to the immune system -> they developed a fungal infection

Question 9

what’s it called when one is born with no functional immune system? and what treatment do they require?

Answer 9

primary immune deficiency

requires bone marrow transplant to be treated or the child will die before their 1st birthday

Question 10

how was a child able to extend their life over a year even though children with primary immune deficiency are expected to die before their first birthday

Answer 10

a patient was put into a sterile plastic bubble, extending his life - he lived for 8 years!

he died after side effects of a bone marrow transplant that wasn’t done well

Question 11

what is the purpose of the immune system?

Answer 11

defence against invaders

self nonself discrimination
- to discriminate against nonself
- exception: fetus

detection of danger/damage
- bacteria/microorganism is not a problem till it harms us and takes away from our resources

to achieve peace and harmony with our enemies

Question 12

what are the components of the immune system? (3)

Answer 12

barriers

cells

soluble molecules (humoral)
—– anything in the blood or in liquid form (outside the cell)

Question 13

what are the barriers of the immune system? (4)

Answer 13

mechanical

chemical

microbiological

nutritional

Question 14

describe mechanical barriers in the immune system (epithelial cells)

Answer 14

epithelial cells are joined by tight junctions that prevent things from going in between the cells

the epithelial cells make up the skin and our inner linings

epithelial cells are also capable of secretions like mucins/mucus and other chemical defences (saliva, tears, etc.)

epithelial cells, especially those of the skin, regenerate and are constantly dividing and replacing dying cells — this is desquamation, shedding that removes anything that may attach to it!

Question 15

what are langerhans

Answer 15

a specialized macrophage that can travel thru the epidermis

Question 16

describe skin as an a example of a mechanical barrier

Answer 16

keratinocytes produced from progenitor cells will produce keratin that hardens forming a keratin shield called the corneal layer

langerhans cell, a specialized macrophage that can travel thru the epidermis

other immune cells are present in the dermis of the skin: mast cells, dermal DC, macrophages…

Question 17

describe the linings of the lungs as an example of a mechanical barrier

Answer 17

goblet cells, a specific type of epithelial cell secretes mucus which lines the lungs and protects us from invaders

cilia is constantly moving material thru lungs — this is why we have the urge to cough and expel materials

Question 18

what are examples of chemical barriers in the immune system?

Answer 18

lysozymes

antimicrobial peptides

fatty acids

Question 19

what are lysozymes?

Answer 19

secreted by epithelial cells

enzymes that digests bacteria and its cell wall – specifically the peptidoglycan component of bacterial cell walls

Question 20

what are antimicrobial peptides?

Answer 20

short positively charged peptides – has antimicrobial properties

there are 21 different antimicrobial peptides in humans

Question 21

how are fatty acids part of the immune’s system chemical barrier?

Answer 21

both saturated and unsaturated fatty acids have antimicrobial properties, inhibiting the growth of bacteria

Question 22

what are defensins?

Answer 22

small molecules used in immunological defense – a chemical barrier

includes:

antimicrobial peptides

fatty acids

Question 23

describe the microbiological barriers in the immune system

Answer 23

most bacteria are not pathogenic do not cause harm - can have positive impacts too!
—- in this case, there’s no DEFENSIVE immune response; immune response is present

environment factors (e.g. diet, maternal) and genetics help shape the microbiome

invaders must compete for resources with bacteria already present in the body

Question 24

describe nutritional barriers in the immune system

Answer 24

microbes need metals, such as iron to function and replicate – needed by their enzymes

to inhibit microbial growth, metals are hidden from microorganisms

Question 25

how is iron a nutritional barrier in the immune system? how do pathogens try to combat this?

Answer 25

in our body, iron is not present in the free state
—— in the cell, iron is complexed with heme, which is bound by hemoglobin
—— iron is actively pimped out of intracellular compartments by NRAMP1 - this removes iron from inside the cell
—— outside the cell, heme is bound haemopexin (HPX)
—— free hemoglobin is bound by haptoglobin (HP) – removes hemoglobin in the blood

to combat this:
bacteria will try to collect the iron by secreting siderophore molecules that bind to the iron to import it back into the bacteria