lymphocyte migration into lymph node

Definition

Target type: biologicalprocess

The movement of a lymphocyte within the lymphatic system into a lymph node, and its subsequent positioning within defined functional compartments such as sites of cell activation by antigen. [GOC:BHF, GOC:pr, PMID:18379575]

Lymphocyte migration into lymph nodes is a critical process in the adaptive immune response, facilitating the encounter of antigen-presenting cells (APCs) with lymphocytes and the initiation of an immune response. This journey involves several stages:

1. **Entry into the Lymph Node:** Lymphocytes enter the lymph node through specialized structures called **high endothelial venules (HEVs)**. These blood vessels have unique cuboidal endothelial cells that express adhesion molecules like **CD34, GlyCAM-1, and PNAd** which bind to **L-selectin** on the surface of lymphocytes. This interaction mediates the initial tethering and rolling of lymphocytes along the HEV wall.

2. **Chemokine-mediated Activation:** Once lymphocytes are rolling on the HEV surface, they encounter chemokines like **CCL21** and **CCL19**, which are secreted by stromal cells within the lymph node. These chemokines bind to **CCR7** receptors on lymphocytes, triggering a signaling cascade that leads to the activation of integrins, particularly **LFA-1**.

3. **Integrin-mediated Adhesion:** Activated LFA-1 on the lymphocyte surface binds to **ICAM-1** on the HEV endothelium, resulting in strong adhesion of the lymphocyte to the vessel wall. This firm adhesion is crucial for the lymphocyte to overcome the shear forces of blood flow and transmigrate through the HEV.

4. **Diapedesis:** The lymphocyte then undergoes diapedesis, a process where it squeezes between endothelial cells and enters the lymph node parenchyma. This process requires the coordinated action of cytoskeletal rearrangements and the involvement of other adhesion molecules like **PECAM-1 (CD31)**.

5. **Migration within the Lymph Node:** Once inside the lymph node, lymphocytes continue their journey towards the T cell zone or B cell zone depending on their type. This migration is guided by chemokine gradients and interactions with stromal cells and other lymphocytes. The chemokines CCL21 and CCL19, along with their receptors CCR7, play a crucial role in directing lymphocytes to their appropriate zones.

6. **Exit from the Lymph Node:** Lymphocytes that fail to encounter their specific antigen exit the lymph node through efferent lymphatic vessels. This ensures that only antigen-specific lymphocytes are retained within the lymph node for an extended period, promoting the development of an immune response.

The intricate process of lymphocyte migration into lymph nodes ensures the efficient delivery of lymphocytes to the site of antigen presentation, enabling the adaptive immune system to respond effectively to diverse pathogens and foreign substances.'
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Proteins (3)

Compounds (14)