Lymphocytes

Question 1

place of B cell development

Answer 1

gestational phase -> embryo and foetal liver
after birth -> only bone marrow

Question 2

2 phases of B cell development

Answer 2

maturation (within the bone marrow) and differentiation (outside the bone marrow)

Question 3

where are memory B cells stored

Answer 3

mostly secondary lymph nodes

Question 4

what process is happenning during B cell development in the bone marrow

Answer 4

selection process - B cells need to be self tolerant

Question 5

in what state do B cells exit the bone marrow

Answer 5

as immature B cells - once they enter circulation = naive B cells

Question 6

what does it mean if a B cell is naive

Answer 6

the B cell has not encountered a foreing antigen yet

Question 7

what phase of B cell development is antigen-dependent

Answer 7

the differentiation - antigen-activated maturation of naive B cells to antibody-secreting plasma cells and memory B cells

Question 8

describe B cell phases during development (considering gene rearrangement)

Answer 8

lymphoid stem cell (DhJh recombination) -> pro-B cell (VhDhJh) -> pre-B cell (VlJl) -> immature B cell -> naive B cell -> mature B cell

Question 9

where does T cell development take place

Answer 9

starts in the bone marrow - immature / progenitor T cells travel to the thymus -> completion of differentiation

Question 10

where do T cells undergo somatic recombination and what is the purpose of this process?

Answer 10

thymus and it is useful for the generation of T cell clones with unique receptors

Question 11

what is a double negative T cell

Answer 11

a progenitor T cell which is not expressing either CD4 or CD8

Question 12

briefly describe T cells development stages

Answer 12

(bone marrow) HSC -> TSP -> (thymic cortex) DN1 -> DN2 -> (subcapsular zone) DN3 - now the cells can differentiate into gamma-delta T cells -> DN4 -> now they start expressing both CD4 and CD8 = DP cells (cortex again - pos selection) -> SP (medulla - neg selection)

Question 13

what is the other name for T cell progenitors

Answer 13

thymic seeding progenitors

Question 14

briefly describe T cell pos selection

Answer 14

junction of cortex and medulla is lined up with epithalial cells which expresses MHC I and II molecules -> DP T cells bind to one of the MHC molecules which determines if the become CD8 or CD4 T cells (if they are unable to bind they undergo apoptosis)

Question 15

what kinase is essential in the positive selection of T cells?

Answer 15

the Lck tyrosine kinase is recruited to the TCR which initiates signalling -> leading to T cell maturation

Question 16

what is negative selection of T cells?

Answer 16

if the T cells bind to stringly to self-MHC molecules they undergo apoptosis

Question 17

clonal selection theory

Answer 17

lymphocyte receptors are produced in billions of different versions (each capable of binding a different ligand) -> once there is an antigen presented by an APC and there is a T cell / B cell that recognizes this antigen –> proliferation and differentiation of activated specific lymphocytes to form a clone of effector cells (so creating a million copies of the same lymphocyte to fight the infection)

Question 18

afferent lymphatic vessels

Answer 18

connects tissues to secondary lymphoid organs

Question 19

efferent lymphatic vessels

Answer 19

connect secondary lymphoid organs to tissues

Question 20

what are high endothelial venules (HEVs) and their function

Answer 20

special venules inside the lymph nodes which allow naive B and T cells to enter the lymph node –> they come from the blood circulation

Question 21

where do B cells reside within a lymph node

Answer 21

in the lymph node follicle

Question 22

what is a germinal centre

Answer 22

a microstructure that forms in secondary lymph nodes -> that is were activated B cells migrate and were they differentiate into plasma cells + proliferate

Question 23

what is the function of the spleen

Answer 23

screens for pathogens in blood

Question 24

what is the differnce between the spleen and lymph nodes?

Answer 24

the spleen has a central arteriole which is constantly sampled for blood pathogens. a lymph node is “supplied” with pathogenic antigens by APCs which deliver them through the aferent lymphatic vessel

Question 25

what is GALT

Answer 25

gut-associated lymphoid tissue

Question 26

what are M cells, where are they located, what is their function?

Answer 26

microfold cells, located in the epithelial lining of the lumen, and their role is to constantly uptake antigens from gut lumen

Question 27

how are antigens from the gut lumen delivered to DCs in GALT

Answer 27

via transcytosis performed by M cells