Lecture 9

Question 1

Secondary Lymphoid Organs

Answer 1

Sites of Adaptive Immune Cells
1. Lymph nodes: screens the lymphatic fluids
2. Spleen: screens the blood
3. MALTs: screens the mucosal surfaces

Question 2

Lymph Nodes

Answer 2

1. Variable sized ‘bean-shaped’ tissues
2. Inline Lymphatic filters
3. Immune surveillance of the Lymphatics

Question 3

Three functional regions

Answer 3

1. Cortex
   a. Lymphoid Nodules (Follicles)
2. Paracortex
3. Medulla
   a. MS: Medullary Sinuses
   includes histiocytes
   b. MC: Medullary Cords
   Ab-secreting plasma cells

Question 4

Lymph Nodes (Roles)

Answer 4

1. Provides a site concentrate B- and T- cells
2. Increases the efficiency of screening for antigens
3. Optimizes B- and T- cell activation

Question 5

Lymph Nodes (Seeding)

Answer 5

1. Naïve lymphocytes (from the bone marrow and thymus) enter the cortex via the vascular supply

Question 6

High Endothelial Venules

Answer 6

1. Most endothelial cells are squamous (flat)
2. High Endothelial Venules are cuboidal in stature and comparatively taller
3. High Endothelial Venules facilitate the translocation of naïve lymphocytes out of the venules and into the sinusoidal spaces of the lymph node cortex

Question 7

Lymph Node (Concentration)

Answer 7

Naïve Lymphocytes segregate and concentrate
1. B-Cells: concentrate in follicles (in the cortex)
2. T-Cells: concentrate in the paracortex

Question 8

Lymph Nodes

Answer 8

1. Lymph enters the Node via the Afferent Lymphatics
2. Lymph starts in the subcapsular sinus
3. Lymph percolates through the body of the node

Question 9

Cortex (Follice)

Answer 9

1. B-Cells
2. Follicular Dendritic Cells

Question 10

Follicular Dendritic Cells

Answer 10

Distinct from the hematopoietic-derived dendritic cells
1. Promote the retention of B-Cells within the Lymph Node Cortex Follicle
2. Promotes the productive movement and interactions of B-Cells within the Lymph Node Cortex Follicle

Question 11

Primary Follicles

Answer 11

NO germinal centers

Question 12

Secondary Follicles

Answer 12

Have germinal centers

Question 13

Differentiation of B-Cells into Plasma Cells

Answer 13

Initial Step in B-Cell Activation
1. Antigen-specific binding to B-Cell Receptor
2. Occurs within the follicle

Question 14

Differentiation of B-Cells into Plasma Cells

Answer 14

Two Fates of Activated B-Cells:
1. Immediately begin developing into plasma cells in a primary focus and the medulla
2. Proliferate into a germinal center within the follicle where the B-cells undergo further enhancement

Question 15

Enhancement of B-Cells in the Germinal Center

Answer 15

Antigen-specific B-Cells proliferate
1. B-Cell Receptor genes undergo somatic hypermutation
2. B-Cell Receptor genes undergo somatic class switch recombination selection
3. B-cells with the highest antigen binding affinity are selected (survive fate)
4. Cells differentiate into Plasma Cells (Ab-producing)
5. Plasma Cells take up residence in the medulla or return to the bone marrow

Question 16

Paracortex

Answer 16

1. T-Cells
2. Dendritic Cells
3. Fibroblast Reticular Cells

Question 17

Fibroblast Reticular Cells

Answer 17

Promote T-Cell interactions with Antigen-Presenting Cells by channeling these cell types along the extended cellular processes

Question 18

Lymph Nodes

Answer 18

Exodus via the Efferent Lymphatics
1. Condition Lymphocytes
2. Antigen-Presenting Cells
3. Antibodies