Homeostatic and pathogenic extramedullary hematopoiesis

Area of Science:

• Hematology
• Developmental Biology
• Immunology

Background:

• Extramedullary hematopoiesis (EH) is blood cell formation outside the bone marrow.
• It occurs during fetal development, immune responses, and pathological conditions.
• EH is a response to diverse changes in the hematopoietic environment.

Purpose of the Study:

• To review the key features of extramedullary hematopoiesis.
• To discuss the regulators involved in major types of EH.

Main Methods:

• Literature review of extramedullary hematopoiesis.
• Synthesis of information on EH in fetal development, immune responses, and myelofibrosis.

Main Results:

• EH occurs in the yolk sac, fetal liver, and spleen during fetal development.
• EH in the spleen and liver supports immune responses by producing antigen-presenting cells and phagocytes.
• Pathological conditions like myelofibrosis can also induce EH.

Conclusions:

• Extramedullary hematopoiesis is a multifaceted process.
• It can be actively or passively induced by various physiological and pathological stimuli.
• Understanding EH regulators is crucial for managing related conditions.