hematopoietikus

Hematopoietikus, or hematopoietic, refers to the processes that generate and regulate blood cells. In humans, most postnatal hematopoiesis occurs in the bone marrow, while during fetal development the liver and spleen contribute to blood cell production. The hematopoietic system maintains steady production of red cells, white cells, and platelets to sustain oxygen transport, immunity, and hemostasis.

Hematopoietic stem cells (HSCs) are rare, self-renewing cells that give rise to all blood lineages. Through a series of progenitor steps, HSCs differentiate into two major pathways: the myeloid lineage (erythrocytes, megakaryocytes/platelets, granulocytes, monocytes) and the lymphoid lineage (B cells, T cells, natural killer cells).

Regulation occurs in bone marrow niches, with signals from cytokines such as erythropoietin (EPO), thrombopoietin (TPO), and granulocyte colony-stimulating factor (G-CSF), guiding lineage decisions. Transcription factors including GATA-1, PU.1, RUNX1, and others orchestrate gene expression programs during differentiation. The process is modulated by the microenvironment and epigenetic changes.

Clinical relevance: Disruption can cause anemia, thrombocytopenia, or leukopenia. Hematopoietic malignancies (e.g., leukemia) arise from transformed hematopoietic cells. Diagnostics include complete blood counts, bone marrow biopsy, flow cytometry, and cytogenetic analyses. Therapies include hematopoietic growth factors (EPO, G-CSF, GM-CSF, TPO mimetics) and hematopoietic stem cell transplantation.

Some conditions show extramedullary hematopoiesis, where liver or spleen contribute to blood cell production, usually in disease states or certain congenital disorders.