Question

Which of the following best describes the process through which lymphocytes gain access to lymph nodes from the blood?

A. Lymphocytes arrest at high endothelial venules (HEV) via integrin binding.
B. Lymphocytes are transported directly from the blood to lymphoid and germinal center follicles.
C. Lymphocytes use B7 (costimulatory molecules) to bind to CD62L and gain access to the lymph nodes.
D. Lymphocytes traverse the endothelial cells of the HEV via transcytosis.

Answer 1

Lymphocytes gain access to lymph nodes from the blood primarily by adhering to and passing through specialized vessels known as high endothelial venules (HEV) via integrin binding.

Step-by-step explanation:

The process through which lymphocytes gain access to lymph nodes from the blood is best described by lymphocytes arresting at high endothelial venules (HEV) via integrin binding, which is option A. Lymphocytes first enter lymph nodes through afferent lymphatic vessels and then encounter specialized post-capillary vessels known as HEVs. These vessels are characterized by their thicker, more columnar endothelial cells. This structure facilitates the passage of lymphocytes from the blood into the lymph node. Lymphocytes use receptor molecules such as L-selectin, which binds to carbohydrate ligands presented by the HEV, leading to adhesion and ultimately extravasation of the lymphocytes into the lymph node where they can respond to antigens.