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Immunity and infection prevention

Innate and adaptive immunity

The main article (“Innate and adaptive immunity”) explains the two “arms” of immunity. This topic goes deeper: which arm do leukaemia and its treatment weaken, and which infections does that make more likely?

Last updated: ~1 min read
Two immune shields
Figure 1.Two immune shields — Innate and adaptive immunity

01Short answer

Innate immunity (skin and mucous membranes, neutrophils, monocytes, complement) works immediately. Chemotherapy and acute leukaemia mainly weaken this arm, especially neutrophils and mucous membranes, so bacterial and fungal infections become more common. Adaptive immunity (T and B lymphocytes and antibodies) is precise and has memory. Steroids, some targeted medicines, antibodies, CAR-T, transplant and CLL weaken this arm; then virus reactivation (for example herpes or CMV), pneumocystis pneumonia and repeated bacterial infections come to the fore.

02Simple explanation

Innate: fast and general.

Adaptive: precise, with memory.

Treatment affects each arm differently.

03Scientific explanation

Prevention: doctors choose antibacterial, antiviral or antifungal prevention according to which arm is weakened.

Teamwork: NCBI/IQWiG explains that the two arms signal to each other, so weakening one affects the other too.

04What happens in the body?

Two shields

One broad and fast, the other precise and with memory.

When neutrophils are low

After chemotherapy, the innate arm weakens; fever is an emergency.

A thinned field of neutrophils.
Figure 2.After chemotherapy, neutrophils thin out.

When lymphocytes are low

Steroids, antibodies, transplant and CLL weaken the adaptive arm; virus and pneumocystis prevention is considered.

Fading gold lymphocytes.
Figure 3.Some treatments lower lymphocytes.

05How the two arms work

Four steps.

Barrier — Skin and mucous membranes.1BarrierSkin and mucous membranes.
Fast response — Neutrophils arrive.2Fast responseNeutrophils arrive.
Precise response — Lymphocytes learn.3Precise responseLymphocytes learn.
Together — The two arms cooperate.4TogetherThe two arms cooperate.

06Which arm, which risk?

Weakened partMore common
NeutrophilsBacterial and fungal infections
Mucous membranesGut and mouth bacteria
T cellsVirus reactivation, pneumocystis
B cells / antibodiesRepeated bacterial infections

07Key terms

Innate immunity
Fast protection present from birth.
Adaptive immunity
Learned, precise protection.
Complement
Proteins that damage microbes.
Reactivation
A hidden virus becoming active again.
Prophylaxis
Preventing infection in advance.

08Key points

  • Immunity has two arms.
  • Chemotherapy mainly weakens the innate arm.
  • Steroids, antibodies and transplant weaken the adaptive arm.
  • The type of risk matches the weakened arm.
  • Your doctor chooses prevention.
  • Fever is always urgent.

09Frequently asked questions

Which of my arms is weak?

It depends on the leukaemia type and treatment; ask your doctor.

Why am I given an antiviral?

When T cells are weakened, hidden viruses can reactivate.

Do the arms recover?

Usually yes: neutrophils quickly, lymphocytes more slowly (“Recovery of immunity”).

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Which of my arms is weak?

  2. Why am I given an antiviral?

  3. Do the arms recover?

My questions

12Sources

  1. InformedHealth.org (IQWiG) via NCBI Bookshelf. The innate and adaptive immune systems
  2. MedlinePlus (U.S. National Library of Medicine). Immune response
  3. National Cancer Institute (NCI). Infection and Neutropenia during Cancer Treatment
  4. Centers for Disease Control and Prevention (CDC). Safer Food Choices for People With Weakened Immune Systems
  5. MedlinePlus (U.S. National Library of Medicine). Blood Differential
  6. MedlinePlus (U.S. National Library of Medicine). White Blood Count (WBC)
  7. American Cancer Society. Infections in People with Cancer
  8. National Cancer Institute (NCI). Monoclonal Antibodies
  9. Annals of Oncology (ESMO), 2016. Management of febrile neutropaenia: ESMO Clinical Practice Guidelines
  10. MedlinePlus (U.S. National Library of Medicine). Blood differential test
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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