Lecture 11

Question 1

Where do immune cells come from and what is the name of the precursor cell they originate from?

Answer 1

bone marrow of long bones, stem cells

Question 2

where do T cells mature?

Answer 2

Thymus

Question 3

where do B cells mature?

Answer 3

bone marrow and other lymphoid organs (spleen)

Question 4

platelet precursor cells

Answer 4

megakaryocytes (after stem cells)

Question 5

types of hematopoietic cells

Answer 5

platelets, B cells, T cells, basophils, eosinophils, neutrophils, monocytes (become macrophages), RBCs

Question 6

name of cells with granules in their cytoplasm?

Answer 6

granulocytes

Question 7

types of cells which are granulocytes

Answer 7

basophil, neutrophil

Question 8

neutrophil nuclei type/shape

Answer 8

lobular nuclei (polymorphonuclear)

Question 9

are lymphocytes the smallest type of immune cell and what is their diameter?

Answer 9

yes, 5-8micrometers

Question 10

how do lymphocytes leave the bloodstream?

Answer 10

squeeze through specialised areas of capillaries called high endothelial venules (HEV)

Question 11

how does lymph from lymph nodes drain back into the bloodstream?

Answer 11

via the thoracic duct

Question 12

function of continuously recirculating lymph

Answer 12

1. ensures appropriate lymphocytes (Naive B and T cells) come into contact with their antigen (and each other)
2. disperses activated lymphocyte cells through the body’s lymphoid tissue

Question 13

what makes lymphocytes antigen-specific?

Answer 13

surface immunoglobulin receptors

Question 14

what cells are antigen-specific, B cells, T cells and/or NK (natural killer) cells?

Answer 14

B and T are antigen-specific

Question 15

what makes NK cells non-antigen-specific?

Answer 15

they lack CD3

Question 16

What TCR receptor(s) do cytotoxic T lymphocytes have that helper T cells don’t have?

Answer 16

cytotoxic cells have CD8, helper T cells have CD4

Question 17

function of Th1

Answer 17

dealing with bacteria/virus

Question 18

function of Th2

Answer 18

deals with parasites/allergies

Question 19

function of Treg

Answer 19

regulatory suppressive T-cells

Question 20

responses of lymphocyte effector subpopulations

Answer 20

antibody production (B lymphocytes), antigen-specific cytotoxicity (CD8/cytotoxic T lymphocytes), ADCC (antibody-dependent cell-mediated cytotoxicity - K cells), natural killer cell activity (NK cells)

Question 21

responses of lymphocyte regulatory subpopulations

Answer 21

cytokine production (CD4 T lymphocytes), helper cells (Th1, Th2, Treg)

Question 22

sequence of responses leading to a secondary response

Answer 22

primary response (if adaptive immune system hasn’t experienced foreign antigen before) –> lag period- the few days before antigen-specific effectors (antibodies/cytotoxic T lymphocytes) appear in the blood (these effectors are temporary and neutralise or remove foreign antigen) –> re-exposure to the same antigen triggers a secondary response (more rapid and vigorous) by the adaptive immune system

Question 23

what happens to the primary response if the antigen is absent for a few days?

Answer 23

it decays

Question 24

how many polypeptide chains make up an antibody (ab) and how are they held together?

Answer 24

4 polypeptide chains (2 heavy and 2 light), held together by disulphide and non-covalent bonds

Question 25

function of variable binding region and constant region

Answer 25

antigen-binding and biological function

Question 26

primary antibody responses are the result of activation of what cells?

Answer 26

virgin (naive), antigen-sensitive B lymphocytes

Question 27

secondary responses are the result of activation of what cells?

Answer 27

memory B lymphocytes

Question 28

function of secondary lymphoid organs

Answer 28

select and bind to antigen-sensitive B lymphocytes that have surface immunoglobulin (sIg) receptors with appropriate affinity

Question 29

what events occur after the activation of antigen-sensitive B cells

Answer 29

proliferation and maturation to produce a population (clone) of plasma cells which secrete soluble antibodies of the same antigen-binding specificity as the sIg on the precursor cell. memory B cells for the sIg on the precursor are also produced as a result of clonal activation and expansion

Question 30

do virgin memory B cells live longer than virgin antigen-sensitive B lymphocytes and is their response faster and larger?

Answer 30

memory B cells live longer and respond more quickly and produce larger secondary responses

Question 31

Naive B cells express what receptor?

Answer 31

CD20

Question 32

What cytokine do helper T cells produce during B cell proliferation?

Answer 32

IL-4

Question 33

what is the receptor on B cells that binds to IL-4?

Answer 33

CD4

Question 34

What receptor do plasma cells express and what is their function?

Answer 34

CD19, produce large amounts of antibodies

Question 35

the four mechanisms through which antibodies work

Answer 35

1. direct neutralisation (of specific molecular interactions - blocks binding of pathogen to body cell by binding to pathogen) 2. complement activation (causes complement cytolysis - complement C1q antibody) 3. opsonisation (enhanced phagocytosis) 4. antibody-dependent cell-mediated cytotoxicity (ADCC) - cell killing of target cell

Question 36

to soluble factors what must the antibody bind to and what must it affect?

Answer 36

receptors, to affect the function of the antigen (prevents the antigen from binding to the target)

Question 37

what regions do phagocytic cells have receptors for?

Answer 37

Fc region of antibody molecules, and C3b activated complement component

Question 38

what is the function of cell-surface receptors on phagocytic cells?

Answer 38

to bind to foreign material coated with antibodies and material with C3b attached to it (for complement activation)

Question 39

what region do Fc-gamma-R's bind to on opsonised IgG?

Answer 39

Fc region

Question 40

Steps of ADCC

Answer 40

1. target cell is opsonised by ab's, Fc portion faces outwards 2. innate NK cells bind to ab Fc region via Fc-gamma-R C3b receptors on their surface (an immunological synapse forms) 3. release of perforin/granzyme --> cytolysis of target cell

Question 41

Do K cells have classical B or T characteristics?

Answer 41

no

Question 42

receptors on K cells

Answer 42

Fc-gamma-R and C3b receptors

Question 43

how do K cells kill cellular material?

Answer 43

short range cytotoxicity

Question 44

what pathways is the complement cascade composed of?

Answer 44

classical and alternative

Question 45

what triggers the classical pathway?

Answer 45

antigen-antibody complexes

Question 46

what triggers the alternative pathway?

Answer 46

bacterial cell wall components

Question 47

result of activation of the complement pathway

Answer 47

1. chemotaxis - attraction of phagocytes to the site of complement activation 2. opsonisation - enhanced phagocytosis 3. lysis - destruction of cell membranes which antibodies are attached to

Question 48

what enzyme do the classical and alternative pathway activate and what is the product?

Answer 48

C3 convertase, C3a and C3b

Question 49

what is the function of C3a?

Answer 49

vasodilation and chemotaxis

Question 50

what is the function of C3b?

Answer 50

opsonisation and membrane lysis

Question 51

sequence of events for antibody-dependent complement-dependent cytotoxicity

Answer 51

opsonisation --> complement C1q binding to IgG Fc complement region --> activation of classical pathway of complement --> MAC (membrane attack complex) formation --> lysis