1. What is the correct order of the four steps in leukocyte trafficking?
A. Rolling → Diapedesis → Activation → Adhesion
B. Rolling → Activation → Adhesion → Diapedesis
C. Adhesion → Activation → Rolling → Diapedesis
D. Activation → Rolling → Diapedesis → Adhesion
B. Rolling → Activation → Adhesion → Diapedesis
2. Leukocyte egress occurs primarily in which part of the circulatory system?
A. Arteries
B. Capillaries
C. Venules
D. Lymphatic ducts
C. Venules
3. What structural characteristic makes venules ideal for leukocyte egress?
A. High blood pressure
B. Thick muscular walls
C. Thin endothelial lining
D. Elastic connective tissue
C. Thin endothelial lining
4. What are High Endothelial Venules (HEVs)?
A. Venules found only in bone marrow
B. Thick tall endothelial cells in lymphoid tissue
C. Flattened endothelial cells in arteries
D. Specialized macrophages
B. Thickt all endothelial cells in lymphoid tissue
5. Which molecule is primarily involved in the rolling step of leukocyte trafficking?
A. Integrins
B. Selectins
C. ICAMs
D. Cytokines
B. Selectins
6. Which molecule acts as a major ligand for selectins?
A. ICAM-1
B. Sialyl Lewis X (SLex)
C. Integrin β2
D. CCL19
B. Sialyl Lewis X (SLex)
7. Which of the following is not a characteristic of chemokines?
A. They regulate immune cell trafficking
B. They act as chemoattractants
C. They bind to ICAMs directly
D. They influence adhesion and activation
C. They bind to ICAMs directly
8. Inside-out signaling primarily affects which molecule type?
A. Selectins
B. Integrins
C. Chemokines
D. ICAMs
B. Integrins
9. ICAMs belong to which molecular family?
A. Chemokines
B. Integrins
C. Immunoglobulin superfamily
D. Selectins
C. Immunoglobulin superfamily
10. Which cells are considered sentinel cells?
A. Naive B cells
B. Dendritic cells and macrophages
C. Neutrophils and eosinophils
D. Endothelial cells only
B. Dendritic cells and macrophages
11. Selectins
Mediate rolling through sugar-binding lectin domains
2. Chemokines
Direct migration via chemical gradients
13. Integrins
Bind to ICAMs; mediate adhesion
14. ICAMs
Ligands for integrins, aid in firm adhesion
15. Describe the four main steps of leukocyte trafficking and the primary molecule(s) involved in each.
- Rolling: Selectins bind mucin-like ligands (Sialyl Lewis X).
- Activation: Chemokines bind receptors → inside-out signaling.
- Adhesion: Integrins bind ICAMs for firm adhesion.
- Diapedesis: Leukocyte crosses the endothelium into tissue.
16. Explain how chemokines and their receptors guide lymphocyte migration into lymph nodes.
Chemokines (CCL19, CCL21) attract lymphocytes expressing CCR7 to lymph node paracortex through HEVs.
17. Compare leukocyte migration at infection sites (myeloid cells) vs. lymphocyte migration in lymphoid tissues.
- Myeloid cells: Move to infection sites via chemotaxis; stay to fight infection.
- Lymphocytes: Travel to lymphoid tissues, get activated, then exit via lymphatics.
18. What is the function of the Fibroblastic Reticular Cell (FRC) network?
Provides structural “roadways” that guide T cells and dendritic cells to meet efficiently in lymph nodes.
19. Define “inside-out signaling” and explain how chemokines initiate it.
Chemokines bind leukocyte receptors → trigger intracellular changes → integrins shift to high-affinity state → firm adhesion to endothelium.
20. What are S1PR1 and S1P, and how do they regulate lymphocyte egress from lymph nodes?
- S1PR1: Receptor on lymphocytes allowing exit from lymph nodes.
- S1P: Lipid chemokine that binds S1PR1 and guides lymphocyte egress.
21. Explain the difference between homotypic binding and heterotypic binding in ICAMs.
- Homotypic: ICAMs bind to other ICAMs (self-binding).
- Heterotypic: ICAMs bind to different molecules (e.g., integrins).
22. What is the role of sentinel cells in the immune response?
Macrophages, dendritic cells, and tissue cells that release cytokines/chemokines upon detecting pathogens → activate leukocyte recruitment.
23. How does the expression of CCR7 and chemokines CCL19/CCL21 direct T-cell and dendritic cell movement?
DCs and T cells expressing CCR7 migrate toward CCL19/CCL21 in the paracortex, bringing them together for antigen recognition.
24. Explain the importance of venule structure in diapedesis.
Thin endothelial walls and slow blood flow allow leukocytes to squeeze through endothelial gaps efficiently.