lymphopoiesis

It is rare now for lymphopoiesis to refer to the creation of lymphatic tissues.

The formation of lymphocytes is known as lymphopoiesis.

Nevertheless, residual T lymphopoiesis continues throughout adult life.

However early in gestation the developing embryo has begun its own lymphopoiesis from the fetal liver.

For example it was thought that the process of lymphopoiesis was a direct, orderly unidirectional sequence.

Lymphopoiesis also arises from the yolk sac.

Lymphopoiesis continues throughout life and so progenitor cells and their parent stem cells must always be present.

This is lymphopoiesis.

The changes were sparked by observations that lymphopoiesis did not always break into two lineages at the level of the CLP.

All are generated by normal or abnormal lymphopoiesis except for certain artificial strains created in the laboratory by development from existing strains.

Taken together, these results strongly suggest that miR-155-5p is an essential molecule in the control of several aspects of hematopoiesis including myelopoiesis, erythropoiesis, and lymphopoiesis.

This model of lymphopoiesis had the virtue of relative simplicity, agreement with nomenclature and terminology, and is still essentially valid for the laboratory mouse.

CLPs subsequently differentiate into B-cells and T-cells in a process designated lymphopoiesis.

The complete loss of or loss of function of any WBC cell type is a serious health matter, but lymphopoiesis is absolutely necessary for life.

Lymphopoiesis can be viewed in a mathematical sense as a recursive process of cell division and also as a process of differentiation, measured by changes to the properties of cells.

A generally regarded valid map of B cell lymphopoiesis is as follows in sequence, in two parts with the first being in the bone marrow and the second in the spleen:.

Changes in cytoplasm, morphology of the cell nucleus, granules, cell internal biochemistry, signaling molecules and cell surface markers are difficult to correlate with definite stages in lymphopoiesis.

However, whatever the details may turn out to be, the process of lymphopoiesis always seems to relentlessly give rise to progeny with special attributes and abilities - "superpowers" so to speak - but with progressively more restricted lymphoid developmental potential.

This is the final stage of B lymphopoiesis but it is the clincher because the plasma cells must either issue antibody close to a source of infection, or disseminate it in the blood to fight an infection at a distance or in an inaccessible part of the body.

Myelopoiesis refers to 'generation of cells of the myeloid lineage' and erythropoiesis refers to 'generation of cells of the erythroid lineage' etc., so parallel usage has evolved in which lymphopoiesis refers to 'generation of cells of the lymphoid lineage'.

B lymphopoiesis occurs exclusively in the bone marrow and B lymphocytes are made continuously throughout life there in a 'microenvironment' composed of stromal cells, extracellular matrix, cytokines and growth factors, which are critical for proliferation, differentiation, and survival of early lymphocyte and B-lineage precursors.

In the case of mammals such as man lymphopoiesis begins with limited passive provision by the mother of lymphocytes and substantial immunoglobulin G that cross the placenta and enter the fetus to provide some protection against pathogens, and also leukocytes that come from breast milk and enter circulation via the digestive tract.

Lymphopoiesis is now used interchangeably with the term "lymphocytopoiesis" - the making of lymphocytes - but other sources may distinguish between the two, stating that "lymphopoiesis" additionally refers to creating lymphatic tissue, while "lymphocytopoiesis" refers only to the creation of cells in that tissue.

Although lymphocytes are usually considered mature (as seen in blood tests) they are certainly not inert but can and do get around the body to anywhere there is a need; and when such need arises, new rounds of 'downstream' lymphopoiesis such as cell multiplication and differentiation may arise, coupled with intense mitotic and metabolic activity.

Lymphocytes have a number of alarming properties such as the ability to wander around the body and take up lodging almost anywhere, and while on the way issue commands in the form of cytokines and chemokines and lymphokines, commands that affect many cell types in the body and which may also recursively induce further lymphopoiesis.