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Question 1

Explain the first line of defence and second line of defence

Answer 1

First line involves antigen uptake and processing by APCS and tcell activation producing cytotoxic T cells, also antibodies circulate
Second line involved bcell activation by T cells and plasma cell formation to produce antibodies

Question 2

What are the major APCS in the storms of organs

Answer 2

Macrophages

Question 3

What are the major APCS of epithelia

Answer 3

Dendritic cells

Question 4

How does interstitial fluid enter the lymphatics- describe the vessels

Answer 4

Via collecting lymph vessels, have valves and sparse smooth muscles

Question 5

What are the two drivers of lymphatic fluid

Answer 5

Smooth muscles rhythmically contracting and move my of tissue during eg exercise

Question 6

From the lymph nodes what does the lymphatic fluid travel in

Answer 6

Larger collecting vessels with spirally arranged smooth muscle
Trucks
Subclavian veins

Question 7

What is the structure of the epithelium of initial lymphatics

Answer 7

Cells are oak leaf shaped held together by adhesive junctions that leave the lobes frees moving
Flaps only allow moment in not out

Question 8

What is the job of the secondary lymphoid organs

Answer 8

Filter lymph for antigen and allow matches before lymphocytes and APCS

Question 9

What is a follicle made up of

Answer 9

Germinal centre and mantle zone

Question 10

In a lymph node what is the first step

Answer 10

Activated macrophage or dendritic cell travel to lymph node and present protein fragments

Question 11

What is the second step in the lymph node

Answer 11

B cells have picked up the antigen in the follicle infested and move to the b/t cell interface

Antigen presentation in the para cortex leads to T cell activation and proliferation

Question 12

What is the third step in lymph nodes

Answer 12

T and b class specific for this antigen meet at the b/t cell zone interface and the t helped cell activates the B cell to proliferate and mature

Question 13

Where are the follicular dendritic cells and what is their job

Answer 13

B cell follicles
Long extensions that form networks, they bind the antigen in native form conformation and present it on their surface for a long time

Question 14

How can an antigen get into the lymph node

Answer 14

A) opsonised by antibody or complement
B) as a small soluble or proteolyzed antic
C) carried by a APC ( dc)

Question 15

If a B cell doesn’t find a match in the follicle what else can it do

Answer 15

Help ferry antigen to FDC’s

Question 16

What is the supporting network or a lymph node made from

Answer 16

Strong trabecular of lymph node and Reticular fibres from reticular cells

Question 17

What are reticular fibres composed of

Answer 17

Collagen 111 and 1

Question 18

What is the free space been the wrapped reticular fibres

Answer 18

Transport venue- conduit for small antigens

Question 19

What is the first step in B cell activation

Answer 19

Either internalise a soluble native antigen or form an immunological synapse with a T cell, if the fitting antigen is part of a larger complex bound to a APC or FDC’s

Antigen attached to the B cell receptor is internalised and transferring a lysosome where it is loaded onto MHC11 ( has come from ER with protective cap- invariant chain- cleaved off in lysosome before loading)

Question 20

What is the second step in B cell activation

Answer 20

Antigen attached to MHC is presented to the T cell at the b/t cell interface

Question 21

What happens if the B cell finds it T cell match

Answer 21

T helper cell activates the B cell to proliferate into
IgM producing plasmablasts
Remaining B cells move to germinal centre for maturation

Question 22

What is the key enzyme generated the mutations and how

Answer 22

Activation induced deaminase
Point mutations in the variable region of the B cell receptor, cleaved off NH2 groups of some cytosines- making it uracil
Uracil is rna equivalent of DNA thymine. In next round of replication, uracil read as thymine, means base pair CG changed to AT

Question 23

Why must the B cell undergo hyper mutation and elimination

Answer 23

Because B cell clone receptor binding to antigen is specific but not super tight, need to select clone with high affinity

Question 24

What at the steps of hyper uracil and elimination

Answer 24

T/b cell interaction at border and receiving of co-stimulators signals
Selected cells enter dark zone of Gc
Undergo somatic hypermuation ( upregulate component of shm machinery and activation of aid)
After 1 or more calves B cells move to light zone
BCRs exposed to antigen by FDC’s
Low affinity ones undergo apoptosis
High affinity ones compete for T cell help
The survivors have three routes

Question 25

What are the three possible routes for a mutated and selected B cell with high affinity

Answer 25

Re enter dark zone for more proliferation and shm
Exit gc as plama cell secreting igG
Exit gc as memory cells

Question 26

What is the turnover of a lymph node

Answer 26

10 to 48 times per day

Question 27

Where do lymphocytes enter and leave lymph nodes

Answer 27

High endothelial venues in the paracortex

Question 28

How can high endothelial venues be recognised

Answer 28

Cuiboidal epithelium compared to squamous

Question 29

What is the tonsils

Answer 29

Ring of lymph follicles - Waldeyers ring

Question 30

What is the lungs innate defence

Answer 30

Mucus containing immunoglobulins mainly igA

Alveolar macrophages