Characteristics
Microscopically, in a Wright's stained peripheral blood smear, a normal lymphocyte has a large, dark-staining nucleus with little to no eosinophilic cytoplasm. In normal situations, the coarse, dense nucleus of a lymphocyte is approximately the size of a red blood cell (about 7 micrometres in diameter). Some lymphocytes show a clear perinuclear zone (or halo) around the nucleus or could exhibit a small clear zone to one side of the nucleus. Polyribosomes are a prominent feature in the lymphocytes and can be viewed with an electron microscope. The ribosomes are involved in protein synthesis, allowing the generation of large quantities of cytokines and immunoglobulins by these cells.
It is impossible to distinguish between T cells and B cells in a peripheral blood smear. Normally, flow cytometry testing is used for specific lymphocyte population counts. This can be used to specifically determine the percentage of lymphocytes that contain a particular combination of specific cell surface proteins, such as immunoglobulins or cluster of differentiation (CD) markers or that produce particular proteins (for example, cytokines using intracellular cytokine staining (ICCS)). In order to study the function of a lymphocyte by virtue of the proteins it generates, other scientific techniques like the ELISPOT or secretion assay techniques can be used.
| CLASS | FUNCTION | PROPORTION | PHENOTYPIC MARKER(S) |
| NK cells | Lysis of virally infected cells and tumour cells | 7% (2-13%) | CD16 CD56 but not CD3 |
| Helper T cells | Release cytokines and growth factors that regulate other immune cells | 46% (28-59%) | TCRαβ, CD3 and CD4 |
| Cytotoxic T cells | Lysis of virally infected cells, tumour cells and allografts | 19% (13-32%) | TCRαβ, CD3 and CD8 |
| γδ T cells | Immunoregulation and cytotoxicity | 5% (2%-8%) | TCRγδ and CD3 |
| B cells | Secretion of antibodies | 23% (18-47%) | MHC class II, CD19 and CD21 |
In the circulatory system they move from lymph node to lymph node. This contrasts with macrophages, which are rather stationary in the nodes.
Read more about this topic: Lymphocyte