Myeloide

Myeloide, in a biological context, refers to the myeloid lineage of blood cells, derived from common myeloid progenitors in the bone marrow as part of hematopoiesis. The term comes from Greek myelos, meaning marrow. In adults, hematopoiesis occurs primarily in the bone marrow, where progenitor cells differentiate along two main branches: the myeloid lineage and the lymphoid lineage.

Cells of the myeloid lineage include erythrocytes (red blood cells), platelets (from megakaryocytes), granulocytes (neutrophils, eosinophils, basophils), monocytes (which become macrophages and some dendritic cells), dendritic cells, and mast cells. These cells play roles in oxygen transport, blood clotting, innate immunity, inflammation, and antigen presentation. The differentiation process is tightly regulated by growth factors and transcriptional programs, with markers such as CD33, CD11b, and others used to identify myeloid cells in research and clinical settings.

Clinically, abnormalities of myeloid development or proliferation lead to a range of disorders. Myelodysplastic syndromes involve ineffective hematopoiesis and dysplasia of myeloid cells; myeloproliferative neoplasms feature excessive proliferation of myeloid cells; and acute myeloid leukemia arises when myeloid precursors fail to mature properly and accumulate. Treatments vary by condition and may include targeted therapies, cytotoxic chemotherapy, and, in some cases, stem cell transplantation.

The myeloid and lymphoid lineages together constitute the major branches of adult hematopoiesis. In embryonic development, early myeloid cells form before bone marrow becomes the primary site of blood formation, with overlapping roles in immune defense and tissue maintenance throughout life.