Lecture 11

Question 1

General Follicle Features

Answer 1

1. High endothelial venules
2. B-Cells concentrated in nodules
3. Germinal centers can form
4. T-Cells in surrounding area

Question 2

Specialized Feature: M Cells

Answer 2

Specialized epithelium that overlies the lymphoid nodules
** Pocket **

Question 3

Structural Features of M Cells

Answer 3

1. Apical membrane lacks dense microvilli
2. Basolateral membrane forms a pocket
3. Leukocytes reside within the pocket
4. Antigens are transcytosed from the lumen into the pocket

Question 4

Foreign Antigen Surveillance

Answer 4

1. Antigens are transcytosed in the pocket
2. B-cells can see concentrated antigens
3. Antigens are processed by dendritic cells for presentations T lymphocytes

Question 5

Foreign Antigen Surveillance

Answer 5

1. B-TH antigens complex transforms B cells into plasma cells
2. Plasma cells secrete IgA antibodies
3. IgA are transcytosed into the lumen by neighboring epithelial cells
4. IgA binds antigen int the lumen
5. IgA binds to apical membrane of M Cells to promote antigen sampling

Question 6

M-Cells

Answer 6

Initiate ‘preventive’ immunology

Question 7

Local Plasma Cells

Answer 7

1. Secrete IgA
2. Enterocytes transcytose IgA

Question 8

TC-Cells

Answer 8

Can take up residence within the epithelial layer

Question 9

Extravasation

Answer 9

Regulated exodus of leukocytes from the vasculature

Question 10

Pro-Inflammatory Cytokines

Answer 10

1. IL-1
2. IL-6
3. TNFa
   vasodilation, vascular permeability

Question 11

Chemokines

Answer 11

IL-8
neutrophil recruitment

Question 12

Rolling and extravasation

Answer 12

1. Rolling
2. Activation
3. Arrest/adhesion
4. Transedothelial migration: diapedesis

Question 13

Selectins

Answer 13

Membrane glycoproteins with a lectin-like domain bind specific glycosylate mucin-like proteins

Question 14

L-Selectin

Answer 14

Present on most circulating leukocytes (asst in rolling) family members bind mucin-like CAMS on endothelia

Question 15

P-Selectin

Answer 15

Inserted on endothelial cells during inflammation promotes the leukocyte adhesion (slow rolling)

Question 16

E-Selecting

Answer 16

Expressed on endothelial cells during inflammation promotes the leukocyte adhesion (slow rolling)

Question 17

Mucin-Like CAMS

Answer 17

1. Heavily glycosylated, serine and threonine-rich proteins
2. Binds selectins

Question 18

Mucin-Like CAMS

Answer 18

Sequesters lymphocytes

Question 19

Rolling

Answer 19

Mediated by selectins binding to mucin-like CAMS
1. Fairly modest adhesion strength
2. Strong enough to have leukocytes - roll along the endothelial surface

Question 20

Rolling (During Inflammation)

Answer 20

1. Cytokines increase abundance of P- and E- selectin on endothelial cells
2. Further slows the rate of rolling

Question 21

P-Selectins

Answer 21

Reserve pool; rapid

Question 22

E-Selectins

Answer 22

De novo synthesis; slow (long term)

Question 23

Activation

Answer 23

1. Activated endothelial cells present chemokines on luminal surface
2. Chemokine binding selects the type of leukocyte that migrate
   ** stop and adhere to surface **

Question 24

Activation

Answer 24

Specific chemokines confer specificity of leukocytes being recruited

Question 25

Neutrophils

Answer 25

IL-8

Question 26

Monocytes

Answer 26

MCP-1

Question 27

T-Cells

Answer 27

CCL-21 CCL-19 CXCL12

Question 28

B-Cells

Answer 28

CXCL13

Question 29

Integrins

Answer 29

1. Heterodimeric proteins: a- and b- chains 2. Large Family of Cell adhesion molecules 3. B2-Integrin: Leukocyte specific integrin

Question 30

LFA-1

Answer 30

aLb2-integrin; regulated adhesion affinity

Question 31

Ig Superfamily CAMS

Answer 31

1. Ligands for b2-integrins 2. Express a range of Ig-like domains 3. Also capable of homotypic binding

Question 32

LFA-1 Activation

Answer 32

1. Chemokine signals specific leukocytes a. Specific leukocytes activate LFA-1 b. LFA-1:ICAM binding stops rolling

Question 33

Arrest-Adhesion

Answer 33

1. Integrins convert to a high affinity conformation a. Strength of adhesion increases markedly 2. Strengthened adhesion fully arrests the rolling leukocyte

Question 34

Migration

Answer 34

1. Signaling changes to migratory phenotype 2. Cells migrate up the chemokine gradient

Question 35

B-Lymphocytes

Answer 35

Follicular dendritic cells reside in the follicle 1. Follicular dendritic cells secrete 'chemokine A' 2. B-cells express a receptor for 'chemokine A' 3. B-cells migrate to the follicles

Question 36

T-Lymphocytes

Answer 36

Fibroblastic reticular cells reside in the paracortex 1. Fibroblastic reticular cells secrete 'chemokine B' 2. T-cells express a receptor for 'chemokine B' 3. T-cells migrate to the paracortex