Leukemia and Immune Suppression: Mechanisms and Consequences

Leukemia compromises immunity through multiple mechanisms:

1. Marrow replacement – malignant clones crowd out normal hematopoiesis → neutropenia, lymphopenia, thrombocytopenia.
2. Dysfunctional leukocytes – malignant cells lack normal immune function; impaired phagocytosis, antibody production, cytotoxic activity.
3. Therapy effects – chemotherapy, steroids, monoclonal antibodies further suppress immunity.
4. Splenomegaly – sequesters platelets/leukocytes; reduced immune surveillance.
5. Immunoparesis – hypogammaglobulinemia (especially in CLL, myeloma) → recurrent encapsulated bacterial infections.
6. T-cell exhaustion – chronic antigen exposure, checkpoint upregulation.

Clinical Impact

• Febrile neutropenia – medical emergency.
• Opportunistic infections (fungal, viral reactivation, PJP).
• Poor vaccine response.
• Autoimmune phenomena (AIHA, ITP) from immune dysregulation.

Infection prophylaxis (antibiotics, antifungals, antivirals), growth factor support, and IVIG are used based on risk stratification.