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Immunity and infection prevention

How leukemia affects immunity

The main article (“How does the immune system work?”) explains how the immune system works. This topic shows how leukaemia itself, even before treatment, weakens your defences.

Last updated: ~1 min read
A few healthy cells among many blasts.
Figure 1.Blasts fill the marrow factory.

01Short answer

Leukaemia is a disease of the bone marrow, the “factory” for immune cells. In acute leukaemias (ALL, AML), immature blast cells fill the marrow and crowd out the production of normal neutrophils, lymphocytes and platelets; even with a high white count, there may be few working defenders. In CLL, the cells look mature but do not make proper antibodies, so antibody levels fall and bacterial infections are common. In the chronic phase of CML, immunity is usually relatively preserved. In hairy cell leukaemia, monocytes and neutrophils are especially low.

02Simple explanation

The factory is full: there is no room for normal cells.

A high white count does not mean strong defence.

Each type weakens defence differently.

03Scientific explanation

Functional neutropenia: in acute leukaemia, the total white count can be high but most cells are blasts that do not fight microbes.

CLL: low antibodies and impaired T-cell function are the main causes of infection.

04What happens in the body?

A crowded marrow

Blasts push out healthy cells, so infection, anaemia and bleeding can all be present at diagnosis.

Looks normal but does not work

CLL cells resemble lymphocytes but do not protect.

Dim, idle lymphocytes.
Figure 2.CLL cells look normal but do not protect.

Four types, four gaps

Acute leukaemias mainly lack neutrophils, CLL lacks antibodies, and hairy cell leukaemia lacks monocytes.

Four shields with different gaps.
Figure 3.Each leukaemia type creates a different gap.

05Leukaemia and defence

Four steps.

Factory — The marrow fills.1FactoryThe marrow fills.
Crowding out — Healthy cells fall.2Crowding outHealthy cells fall.
Gaps — Defence weakens.3GapsDefence weakens.
Treatment — Space opens up.4TreatmentSpace opens up.

06Leukaemia type and immune gap

TypeMain gap
ALL / AMLNeutrophils and all normal cells
CLLAntibodies, T-cell function
CML (chronic phase)Usually relatively preserved
Hairy cellMonocytes and neutrophils

07Key terms

Blast
An immature cell.
Functional neutropenia
Neutrophils present but not working.
Bone marrow
The tissue where blood cells are made.
Hypogammaglobulinaemia
A shortage of antibodies.
Cytopenia
A shortage of blood cells.

08Key points

  • Leukaemia weakens the immune “factory”.
  • A high white count is not strong defence.
  • Each leukaemia type creates its own gap.
  • Antibodies are often low in CLL.
  • With treatment, healthy cells can return.
  • Protection starts at diagnosis.

09Frequently asked questions

My white count is high; why am I prone to infection?

Because many of those cells may be non-working leukaemia cells.

Should I take care even before treatment?

Yes, especially in acute leukaemia and CLL.

Will treatment restore immunity?

As the leukaemia is controlled, normal cells usually return (“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. My white count is high; why am I prone to infection?

  2. Should I take care even before treatment?

  3. Will treatment restore immunity?

My questions

12Sources

  1. National Cancer Institute (NCI). Infection and Neutropenia during Cancer Treatment
  2. MedlinePlus (U.S. National Library of Medicine). Immune System and Disorders
  3. American Cancer Society. Infections in People with Cancer
  4. National Cancer Institute (NCI), SEER Training. Introduction to the Lymphatic System
  5. InformedHealth.org (IQWiG). What are the organs of the immune system?
  6. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: neutropenia
  7. National Cancer Institute. NCI Dictionary of Cancer Terms: cytokine
  8. Cancer Research UK. Your blood, bone marrow and cancer drugs
  9. American Cancer Society. Neutropenia (Low White Blood Cell Counts)
  10. NHS. How to wash your hands
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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