Blood Cell Lineages

From multipotent hematopoietic stem cells in the bone marrow.

From where do all the cellular elements of the blood arise?

Common lymphoid progenitor cells and common myeloid progenitor cells

What are the two main types of stem cells produced by multipotent hematopoietic stem cells?

Innate lymphoid cells (ILCs), natural killer (NK) cells, and lymphocytes (T and B cells).

What cell types arise from the common lymphoid progenitor?

Erythrocytes, megakaryocytes (platelet producers), monocytes, dendritic cells, neutrophils, eosinophils, basophils, and mast cells.

What cell types arise from the common myeloid progenitor?

They have antigen receptors and specific sites of differentiation—T cells in the thymus, B cells in the bone marrow.

What differentiates T and B lymphocytes from other leukocytes?

Antibody-secreting plasma cells.

Into what do B cells differentiate after antigen encounter?

Effector T cells with diverse immune functions.

Into what do T cells differentiate after antigen encounter?

They lack antigen specificity.

How do ILCs and NK cells differ from T and B lymphocytes?

Neutrophils, eosinophils, and basophils; named for cytoplasmic granules visible in blood smears.

What are granulocytes and why are they named so?

Because of their irregularly shaped (multi-lobed) nuclei.

Why are granulocytes also called polymorphonuclear leukocytes?

They are phagocytic and enter tissues; mature after encountering a potential pathogen.

What is the role of immature dendritic cells?

Mainly from the common myeloid progenitor, though some also arise from the common lymphoid progenitor.

From which progenitors do most dendritic cells arise?

They differentiate into macrophages or dendritic cells.

What happens when monocytes enter tissues?

They enter tissues and complete their maturation there.

What happens to mast cells after they leave the blood?

Produce platelets important in blood clotting.

What function do megakaryocytes perform?

Cytoplasmic granules

Small vesicles in granulocytes that contain enzymes and chemicals used to destroy pathogens. Their staining gives neutrophils, eosinophils, and basophils their distinctive appearance in blood smears.