Lymphocytes make up 1/4 to 1/3 of the leukocytes in the peripheral blood.
Lymphocyte as a term is most often used with the meaning of the immunologically (immunopoietically) directed cell.
Together with the lymphoid organs, lymphocytes make the immunological lymphocytic system.
The cells of this system, like other hematopoietic cells, develop from the common stem cell in the bone marrow. Some lymphocytes originate in the germinative centers of the lymph nodes.
Primary lymphoid organs (bone marrow and thymus) form immature lymphocytes. Maturation of immature lymphocytes begins in them.
Depending on the antigen, the maturation of lymphocytes continues in the peripheral lymphoid organs (lymph nodes, spleen, tonsils, appendix, and Peyer’s patches), from where, with the help of the lymph, lymphocytes can reach the peripheral blood again.
The peripheral blood is just a transmitting vehicle. The cells of the immunological system in the peripheral blood have the morphology of the lymphocytes, and morphologically are very similar to each other, but they differ both in the direction of differentiation and the stage of maturation. The existence of specific markers on the lymphocyte membrane (CD-antigens) has enabled the differentiation of lymphocytic subpopulations.
The largest number of the lymphocytes in the peripheral blood belongs to the subpopulations of the mature T-cells. A considerable smaller number of the lymphocytes belong to mature B-cells. The precursors of T- and B-cells are of the least number.
Lymphoblast is the earliest morphologically recognizable cell of the lymphocytic lineage.
During the lymphocytopoiesis, three developing cell forms can be seen.
In the blood there are some types of lymphocytes that can be morphologically recognized: the peripheral blood has 85% of T-lymphocytes and 15% of B-lymphocytes. |
