Overview
Every day about 3 liters of fluid leak from capillaries into the tissues. Lymphatic vessels collect this fluid (lymph), filter it through lymph nodes and return it to the blood through the thoracic duct and right lymphatic duct into the subclavian veins. Lacteals in the intestine also absorb dietary fat.
Primary lymphoid organs produce and train immune cells: the red bone marrow (B cells) and the thymus (T cells). Secondary organs are where immune responses happen: lymph nodes, the spleen, tonsils and lymphoid tissue in the gut. The 3D body shows the spleen and thymus; the lymph node study shows the inside of a node.
Main functions
- Returning excess tissue fluid to the circulation
- Absorbing fats from the small intestine
- Filtering lymph and blood to trap microorganisms
- Producing and maturing white blood cells
- Mounting innate and adaptive immune responses
Key structures
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Spleen
The largest lymphoid organ, filtering blood and removing old red blood cells.
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Thymus
A gland in the upper chest where T lymphocytes mature.
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Lymph nodes
Bean-shaped filters along lymphatic vessels that trap microbes and activate immune cells.
Lymph flow and immune defense
Lymph moves slowly, pushed by muscle contraction, breathing and one-way valves. In each lymph node, macrophages engulf debris and microbes while lymphocytes inspect antigens. When an infection is present, nodes swell as lymphocytes multiply.
Innate immunity (skin, inflammation, neutrophils, macrophages) acts within minutes. Adaptive immunity takes days: B cells make antibodies and T cells kill infected cells and coordinate the response, then leave memory cells that make the next response faster. Vaccines use this memory.
Nursing assessment
- Palpate lymph nodes of the head, neck, axillae and groin: note size, tenderness, mobility and consistency.
- Tender, mobile nodes suggest infection; hard, fixed, painless nodes are concerning for cancer.
- Assess for signs of infection: fever, redness, swelling, drainage; older adults may only show confusion.
- Ask about allergies and previous reactions to drugs, foods, latex and blood products.
- Measure limb circumference when lymphedema is suspected.
Common conditions
| Condition | What happens | Key signs | Nursing priorities |
|---|---|---|---|
| Lymphedema | Swelling from blocked or removed lymphatics (for example after breast cancer surgery) | Firm swelling of a limb, heaviness | No BP, injections or blood draws in the affected arm; elevation, compression and skin care |
| Anaphylaxis | Severe type I hypersensitivity reaction | Hives, wheezing, stridor, swelling of the lips and tongue, hypotension | Stop the trigger, maintain airway, give IM epinephrine immediately, then oxygen and fluids |
| HIV infection | Virus that destroys CD4 T cells | Progressive immunodeficiency with opportunistic infections when untreated | Antiretroviral adherence, standard precautions, infection prevention |
| Lymphoma | Cancer of lymphocytes | Painless enlarged nodes, fever, night sweats, weight loss | Chemotherapy care, neutropenic precautions |
| Splenic rupture | Tear of the spleen after trauma or in mononucleosis | Left upper quadrant pain, left shoulder pain (Kehr's sign), shock | Monitor for hemorrhage; teach clients with mononucleosis to avoid contact sports |
| Systemic lupus erythematosus | Autoimmune disease affecting many organs | Butterfly rash, joint pain, fatigue, kidney involvement | Sun protection, infection prevention on immunosuppressants, monitor kidney function |
Labs and normal values
| Test | Typical adult range | Why it matters |
|---|---|---|
| White blood cell count | 5,000–10,000/mm³ | High in infection and inflammation; low with chemotherapy and bone marrow failure |
| Absolute neutrophil count | 2,200–7,700/mm³ | Below 1,000 needs neutropenic precautions; below 500 means severe risk |
| CD4 count | 500–1,500 cells/mm³ | Below 200 defines AIDS |
| C-reactive protein | Below 1.0 mg/dL | Marker of inflammation |
| Platelets | 150,000–400,000/mm³ | Low after splenic sequestration or bone marrow suppression |
Reference ranges differ between laboratories and textbooks. Use the values your program and facility use.
Exam tips
- Epinephrine is the first drug for anaphylaxis; antihistamines and steroids are add-ons, not substitutes.
- After a splenectomy, clients need vaccines (pneumococcal, meningococcal, Hib) and must report fevers promptly.
- A left shoulder pain after abdominal trauma (Kehr's sign) suggests blood under the diaphragm from the spleen.
Practice questions
8 NCLEX-style questions on the lymphatic & immune system. Pick an answer to see the rationale.
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A client develops wheezing, lip swelling and hypotension minutes after an IV antibiotic starts. What is the first drug the nurse expects to give?
Show the answer and rationale
Answer B: Epinephrine. Epinephrine reverses bronchospasm and hypotension in anaphylaxis. Stop the infusion first.
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A client had a left mastectomy with axillary node removal. Which instruction is correct?
Show the answer and rationale
Answer B: Avoid injections and blood draws in the left arm. Removing nodes impairs lymph drainage; trauma or constriction can trigger lymphedema.
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Which lab result requires neutropenic precautions?
Show the answer and rationale
Answer B: ANC 800/mm³. An absolute neutrophil count below 1,000/mm³ greatly increases infection risk.
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After blunt abdominal trauma, a client reports left shoulder pain. The nurse suspects injury to the:
Show the answer and rationale
Answer B: Spleen. Blood from a ruptured spleen irritates the diaphragm and refers pain to the left shoulder (Kehr's sign).
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Which organ is where T lymphocytes mature?
Show the answer and rationale
Answer B: Thymus. T cells are made in the bone marrow but mature in the thymus.
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Which lymph node finding is most concerning for malignancy?
Show the answer and rationale
Answer B: Hard, fixed, painless node. Malignant nodes are typically hard, painless and fixed to surrounding tissue.
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Which teaching is most important after a splenectomy?
Show the answer and rationale
Answer B: Report fever promptly and keep vaccinations up to date. Asplenic clients are vulnerable to severe infections from encapsulated bacteria.
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A CD4 count below which value defines AIDS?
Show the answer and rationale
Answer C: 200 cells/mm³. A CD4 count below 200 cells/mm³ (or certain opportunistic infections) defines AIDS.