Lecture 8

Question 1

Primary Lymphoid Organs

Answer 1

Sites of Immune Cell Development
1. Bone Marrow: genesis of all immune cells
a. B-Cell maturation
2. Thymus:
b. T-Cell maturation

Question 2

Secondary Lymphoid Organs

Answer 2

Sites where Adaptive Immune Cells are activated and initiate function (mature-naïve to activated)
1. Spleen: filters the blood
2. Lymph Nodes: keeps from going systemic
3. MALTs: screen lymphatic tissue

Question 3

Tertiary Lymphoid Organs

Answer 3

1. Peripheral sites with persistent infection
2. Immune cells take up residence

Question 4

Vascular and Lymphatic Vessels

Answer 4

1. Connect the Immune system
2. Vascular System: deliver immune cells throughout the body
3. Lymphatic System: drain peripheral tissue effluent through lymph nodes; return to blood

Question 5

Bone Marrow

Answer 5

Bones with greatest level of RBC/WBC synthesis
1. ileum: hip
2. femur: leg
3. sternum: chest
4. humerus: arm

Question 6

Bone Marrow

Answer 6

Specialized environment that promotes the homing, proliferation, and differentiation of hematopoietic stem cells

Question 7

Developmental Niches (Cues from Four Cell Types in Bone)

Answer 7

1. Osteoblasts: generate bone matrix
   a. signal and moderate HSC differentiation
2. Endothelial Cells: line vascular spaces
   a. signal and moderate HSC differentiation
3. Perivascular and Reticular Cells: cellular processes bridge bone to blood vessels
   a. signal and moderate HSC differentiation
4. Sympathetic Neurons: moderate release of hemopoietic cells from marrow

Question 8

Hematopoietic Stem Cells (HSC)

Answer 8

Give rise to all cell types in the immune system

Question 9

Endosteal Niche

Answer 9

Leukocyte precursors are sequestered prior to development

Question 10

Osteoblasts

Answer 10

Interact with stem cells to promote quiescence

Question 11

Vascular Niche

Answer 11

HSCs Induced to proliferate and differentiate

Question 12

Reticular Cells

Answer 12

Cellular ‘Mesh’; traffic HSCs between sites

Question 13

Bone Marrow

Answer 13

Immature lymphocytes

Question 14

Thymus

Answer 14

Thymocytes

Question 15

Thymus

Answer 15

Mature Naïve T-Cells

Question 16

2o Lymphoid Organs

Answer 16

Mature Naïve T-Cells

Question 17

Thymus Cortex

Answer 17

Site of Thymocyte proliferation and selection

Question 18

Thymus Medulla

Answer 18

Reserve of Mature (Naïve) T-Cells

Question 19

T-Cell Development, Differentiation, and Selection

Answer 19

1. Immature lymphocytes are delivered to the subcapsular cortex (thymocytes)
2. Thymocytes are induced to undergo proliferation
3. Thymocytes develop T-Cell receptors on their surface

Question 20

T-Cell Development, Differentiation, and Selection

Answer 20

1. Thymocytes interact with the stromal epithelial reticular cells
2. Thymocytes migrate toward the medulla while undergoing selection
3. Functional but NOT ‘self-reactive’ thymocytes are selected to be mature T-cells
4. Mature T-Cells reside in the medulla
5. Cytokines signal for their medullary release and migration into the vasculature

Question 21

DN

Answer 21

Double-negative cells

Question 22

DP

Answer 22

Double-positive cells

Question 23

SP

Answer 23

Single-positive cells

Question 24

Negative Selection

Answer 24

Thymocytes bind with too high an affinity to stromal cells expressing MHC: Self-Antigen Complexes

Question 25

Positive Selection

Answer 25

Thymocytes bind with an intermediate affinity to stromal cells expressing MHC: Self-Antigen Complexes

Question 26

Expansion

Answer 26

1. Undergo extensive proliferation -- Symmetrical Cell Division 2. Generate antigen receptors unique to each individual cell -- T-Cell Receptors

Question 27

Selection:

Answer 27

1. Remove thymocytes that strongly recognize self-antigens 2. Retain thymocytes that are capable of antigen recognition

Question 28

Vascular and Lymphatic Vessels

Answer 28

1. Connect the immune system and organs 2. Pathway for immune cell distribution 3. Pathway for pathogen: immune convergence