Lymphopoese

Lymphopoiesis is the process by which lymphocytes, including B cells, T cells, and natural killer (NK) cells, are produced and mature. It is a component of hematopoiesis, the formation of all blood cells, and is distinguished by its focus on lymphoid-lineage cells.

In humans, early lymphoid cells originate from hematopoietic stem cells in the bone marrow, which give rise to common lymphoid progenitors. B cells complete their maturation largely in the bone marrow, while most T cell precursors migrate to the thymus to mature.

Within the thymus, T cell precursors undergo rearrangement of their T cell receptors and undergo selection processes that shape the repertoire of naive T cells. NK cells also arise from lymphoid progenitors, primarily in the bone marrow, and migrate to peripheral tissues where they contribute to innate immune responses.

Lymphopoiesis is regulated by cytokines and transcription factors. Interleukin-7 (IL-7) is crucial for lymphoid survival and development, and FLT3 ligand supports early lymphoid progenitors. Lineage commitment involves transcription factors such as PAX5 for B cells and NOTCH signaling for T cells, guiding progenitors toward their final mature phenotypes.

Age-related thymic involution reduces T cell output, with peripheral expansion of mature lymphocytes partially compensating. Lymphopoietic disorders include lymphopenia, while malignant lymphoid neoplasms such as lymphomas and leukemias arise from lymphoid cells.