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IMMUNE TISSUES

Lymph
Nodes

Filtering Threats. Activating Immunity.

Lymph nodes are small, bean-shaped structures that act as immune hubs. They filter lymph fluid, trap pathogens, and bring together immune cells — including dendritic cells, T cells, and B cells — to initiate and coordinate adaptive immune responses.

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What Are Lymph Nodes?

Lymph nodes are small, bean-shaped organs distributed throughout the body, particularly in the neck, armpits, chest, abdomen, and groin. They are part of the lymphatic system and filter lymph fluid, trapping pathogens, debris, and abnormal cells.

Inside lymph nodes, antigen-presenting cells such as dendritic cells capture and process antigens, then activate T cells in the paracortex and B cells in the follicles. This interaction initiates adaptive immune responses and supports the generation of long-lived memory B and T cells.

Lymph nodes are essential for detecting infections early, coordinating immune responses, and maintaining long-term immune memory.

Lymph nodes at a glance

Type of tissueSecondary lymphoid organ
Main roleFilter lymph, activate adaptive immunity
Where it isThroughout the body (e.g., neck, armpits, chest, abdomen, groin)
LifespanFunctional throughout life (may decline with age)

Key Functions of Lymph Nodes

Lymph nodes perform several essential functions that help keep the immune system vigilant and effective.

1. Filter lymph fluid

Trap and help eliminate pathogens, abnormal cells, and debris from the lymph before it returns to the circulation.

2. Activate T cells

Dendritic cells present antigens to naïve T cells, leading to their activation, proliferation, and differentiation into effector and memory T cells.

3. Activate B cells

Support B cell activation, germinal center reactions, antibody production, and the generation of long-lived memory B cells.

4. Coordinate immune responses

Bring together different immune cells to ensure a coordinated and effective adaptive immune response.

Anatomy and Structure

Lymph nodes are organized into distinct regions, each with a specialized function.

Afferent lymphatic vessel(brings lymph from tissues)
Subcapsular sinus(traps antigens and particles)
B cell follicle(site of B cell activation)
Germinal center(site of B cell proliferation and antibody maturation)
Capsule(connective tissue layer)
T cell zone (paracortex)(site of T cell activation)
Medullary cords(contain plasma cells, macrophages, and antibodies)
Efferent lymphatic vessel(returns lymph to circulation)
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  1. Afferent lymphatic vessel

    Brings lymph from tissues.

  2. Subcapsular sinus

    Traps antigens and particles.

  3. B cell follicle

    Site of B cell activation.

  4. Germinal center

    Site of B cell proliferation and antibody maturation.

  5. Capsule

    Connective tissue layer.

  6. T cell zone (paracortex)

    Site of T cell activation.

  7. Medullary cords

    Contain plasma cells, macrophages and antibodies.

  8. Efferent lymphatic vessel

    Returns lymph to circulation.

Lymph Nodes and Aging

A resilient immune system today
for healthier tomorrows.

With age, several changes can occur in lymph nodes:

  • Reduced cellularity and architectural changes.
  • Decreased naïve T cell input.
  • Altered B cell responses and smaller germinal centers.
  • Accumulation of senescent cells and chronic low-grade inflammation.
  • These changes can contribute to immunosenescence and a reduced ability to respond to new infections and vaccines.

Lymph Nodes in Health and Disease

InfectionsBecome enlarged (swollen) during infections as immune cells proliferate.
Autoimmune diseasesMay show persistent activation and architectural changes.
CancerCan be sites of metastasis for several cancers (e.g., breast, melanoma, lymphoma).
LymphedemaDamage or removal of lymph nodes (e.g., during cancer surgery) can impair lymphatic drainage, leading to lymphedema.
VaccinationLymph nodes are key sites for generating antibody and memory T cell responses after vaccination.

The good news

Healthy lifestyle choices — including regular physical activity, a balanced diet, adequate sleep and stress management — can support healthy lymph node function at any age.

Learn more about aging & immunity   →

Selected sources and references

Artwork illustrates the main mechanisms schematically; molecular sizes, colors and distances are not literal.