More Host defence

Question 1

what is an antigen

Answer 1

molecule capable of inducing an adaptive immune response

Question 2

what do antigen presenting cells do

Answer 2

taste the environment, phagocytose foreign material, process and present antigen in lymphoid tissue

Question 3

what are the properties of adaptive immune response

Answer 3

diversity and specificity, seld-tolerance, memory

Question 4

describe the process of Tc cells

Answer 4

APC ingests bug, bug antigen and MHC molecule displayed on APC surface, CD8 cells activated and become cytotoxic, and bind to infected cells
perforin makes holes in the infected cell membrane and infector cell lyses

Question 5

describe the process of Th cells

Answer 5

APC ingests bug, antigen displaced in APC surface with MHC2, interactions with cell receptor and co-inhibitory/ stimulatory receptors release cytokines, induces B cell activation and CD4 cells differentiated into specific Th subtype

Question 6

where are MHC 1 molecules found

Answer 6

on all nucleated cells

Question 7

where are MHC 2 found

Answer 7

only on macrophages, dendritic cells and B cells

Question 8

what are B cells

Answer 8

type of lymphocyte involved in antibody production

Question 9

where are B cells made and stored

Answer 9

made in bone marrow, stored in secondary lymphoid organs

Question 10

describe IgM

Answer 10

secreted by immatured plasma cells, CSR; variable region unchanged, attached to different constant region so changed properties
good at neutralising/ agglutinating
looks like a ring

Question 11

describe IgA

Answer 11

can access musocsal surface, mediates mucosal immunity, good at opsonising and fixing complement
double pronged

Question 12

describe IgG

Answer 12

makes up > 80% of circulating antibodies
constant region can activate complement and interact with phagocytes
good at opsonising and fixing complement

Question 13

describe IgE

Answer 13

binds mast cells

mediates allergic response

Question 14

what is CSR

Answer 14

Class switch recombination; sequential excision of constant region DNA means same plasma cells secrete different class of antibody with same specificity

Question 15

what controls CSR

Answer 15

cytokines

Question 16

describe the effector function of antibodies

Answer 16

variable region binds to target antigen and constant region interacts with effectors

Question 17

what causes chronic inflammation

Answer 17

irritating cause persists, cellular response is inappropriate, structural abnormalities

Question 18

describe the pattern of chronic suppurative inflammation

Answer 18

mostly innate cells (neutrophils) often surrounded by capsule of chronic inflammatory cells/ fibrous tissue e.g. lung abcess

Question 19

describe the pattern of chronic autoimmune inflammation

Answer 19

mostly cells of adaptive immune system, may lead to fibrosis e.g. rheumatoid arthritis, smoking leading to fibrosis

Question 20

describe the pattern of chronic granulomatous inflammation

Answer 20

mostly cells of adaptive immune system, may lead to fibrosis caused by infection, foreign body, aberrant inflammation, unknown origin e.g. sarcidosis

Question 21

what is a granuloma

Answer 21

small nodule composed of organised collection of macrophages surrounded by dense collection of lymphocytes and fibroblasts

Question 22

what is a hypersensitive reaction

Answer 22

disease where immune response to environmental antigens causes inflammation and damage to the body itself

Question 23

what is a type 1 hypersensitivity reaction

Answer 23

IgE; immunological memory to something leading to allergic response

• immediate and acute
• e.g. acute anaphylaxis, hay fever

Question 24

describe what happens during a type 1 hypersensitivity reaction

Answer 24

allergen binds to IgE coating mast cells in skin
mast cell contain granules that contain mediators that active immune system e.g. histamine, cytokines, basophils
binding of mast cells to IgE links them and signalling pathway made so they degranulate

Question 25

what is the classification used for hypersensitivity reactions

Answer 25

Gell and Coombes

Question 26

what is a type 2 hypersensitivity reaction

Answer 26

IgM/ G bind to cell surface antigens

• fairly quick
• leads to tissue injury and altered receptor function
• e.g. transfusion reactions, autoimmune disease

Question 27

what is a type 3 hypersensitivity reaction

Answer 27

immune complexes leading to activation of complement

• antibodies and targets circulate, little lumps of antibodies and target get deposited in skin/ lung/ kidneys etc leading to activation of immunity and tissue damage
• e.g. farmers lung, SLE, post-streptococcal GN

Question 28

what is a type 4 hypersensitivity reaction

Answer 28

T cell mediated delayed type hypersensitivity (DTH)

• formation of granulomas so slow process
• depends on activation of T cells which secrete cytokines when activated by antigens
• e.g. TB, contact dermatitis

Question 29

how to remember hypersensitivity reactions

Answer 29

ACID
allergic
cytotoxic killing
immune complexes
delayed T helper cells

Question 30

what is inflammation

Answer 30

local response to infection or injury

Question 31

what is the main function if inflammation

Answer 31

destroy/ inactivate foreign invaders, set the stage for tissue repair

Question 32

what are the key mediators in inflammation

Answer 32

phagocytes

Question 33

what are the basic stages of inflammation

Answer 33

bacteria introduced, Chemomediates cause vasodilation and capillary permeability
chemoattractants recruit neutrophils to area
diapedesis results in neutrophils entering tissue where they engulf and phagocytose bacteria
capillaries return to normal as neutrophils continue to clear infection

Question 34

what initiates acute inflammation in the lungs

Answer 34

specialist tissue resident macrophages = alveolar macrophages

Question 35

how do alveolar macrophages start the process of inflammation in the lungs

Answer 35

respond to pathogens etc by recognising PAMPs and DAMPs

Question 36

what type of reaction is anaphylaxis

Answer 36

type 1 hypersensitivity reaction

Question 37

atopy definition

Answer 37

genetic tendency to exaggerated IgE response to antigen