The stages of lymphocytic lineage development are presented in Diagram of hematopoiesis

Various lymphocytic types and their precursors are similar in terms of morphology; however it is feasible to identify them by certain specific plasma membrane markers

• are called large lymphocytes because of their size (10-18 μm)
• have rounded or bean-shaped nuclei with finely dispersed chromatin
• have a slightly basophilic cytoplasm of a considerable volume

• are called medium lymphocytes because of their size (8-9 μm)
• have rounded or bean-shaped nuclei with heterochromatin clumps
• have a slightly basophilic cytoplasm of a smaller volume

• are called small lymphocytes because of their size (6-7 μm)
• have rounded nuclei or nuclei with invaginations; the nuclei are dense (heterochromatin prevails) and occupy the largest part of the cells
• have a slightly basophilic cytoplasm that forms narrow rims around the nuclei

T cell development continues in the thymus where the cells are categorized into killer T cells and helper T cells then migrating to other tissues.

B cells migrate from the bone marrow into lymphoid tissue turning into plasma cells. These cells are also present in the red bone marrow.

NK cells become completely mature in myeloid tissue.

Lymphoblasts (large lymphocytes) q.v. #1, #2, #3. Medium (immature) lymphocytes q.v. #1, #2, #3. Small (mature) lymphocytes q.v. #1, #2, #3, #4. Plasma cells q.v. #1, #2

The stages of monocytic lineage development are presented in Diagram of hematopoiesis

• are large cells 12-18 μm in diameter
• have rounded or slightly concave nuclei
• have basophilic cytoplasm with sparse azurophilic granules
• are able to divide

• are up to 20 μm in diameter
• have bean-shaped or horseshoe-shaped nuclei
• have basophilic cytoplasm with small azurophilic granules
• migrate to the blood and then to other tissues to become macrophages or dendritic antigen-presenting cells; macrophages are found in the red bone marrow

Promonocytes q.v. #1, #2. Promonocytes q.v. #1, #2