The Lineages of Blood Cells in Humans

All the blood cells in your body are derived from precursor cells that originate in the bone marrow

By Amirali Banani | April 13, 2023

All blood cells in the human body originate from a multipotential hematopoietic stem cell (known as a hemocytoblast). As its name suggests, it has the potential to differentiate into any type of blood cell — whether that be a red blood cell, neutrophil or B-lymphocyte. The hemocytoblast originally differentiates into two progenitors, the common myeloid progenitor and the common lymphoid progenitor, from which two separate series of cells originate.

The common myeloid progenitor differentiates into megakaryocytes, erythrocytes (a.k.a red blood cells, which transport oxygen and account for 99% of all blood cells), mast cells, and myeloblasts. Megakaryocytes then form thrombocytes (platelets), responsible for blood clotting, through fragmentation. Myeloblasts, meanwhile, form basophils, neutrophils, eosinophils — mature white blood cells called granulocytes — and monocytes. Monocytes then further differentiate into macrophages, the main cell of the innate immune system that kills pathogens through phagocytosis.

On the other hand of the “blood cell lineage spectrum”, the common lymphoid progenitor differentiates into natural killer cells — the cells of the innate immune system that destroy diseased and virally-infected cells of the body — as well as small lymphocytes. The small lymphocytes then further differentiate into B-lymphocytes and T-lymphocytes, the two primary cells of the adaptive immune system. T-lymphocytes direct immune responses against foreign antigens that enter the body, while B-lymphocytes when activated differentiate into plasma cells which secrete antibodies that bind to these antigens and neutralize them. These lymphocytes are also responsible for developing immunologic memory which allows the adaptive immune system to quickly recognize and eliminate pathogens through their antigens should they enter the body again.

Together, these matured blood cells sustain cellular survival through the transport of oxygen and nutrients, hinder excess blood loss through the formation of blood clots, and keep the body safe from dangerous pathogens that can potentially inflict extensive damage on the cells that keep us alive.