Lymphocyte
A lymphocyte is a cell that belongs to group of white blood cells (i.e., leukocytes), which are a major component of the immune system. The group broadly breaks into B-lymphocytes and T-lymphocytes. [1]
B-lymphocyte
These are cells involved in the production of antibiodies (i.e., the humoral immune response. They have no relationships to the B- or Beta-cells of the pancreas.
T-lymphocyte
Lymphocytes of these types directly destroy appropriate target cells, or help generate cells that do.
=T4 Helper Cells
T-lymphocytes with the T4 protein on their surface which recognizes the antigenic peptide while the CD4 molecule recognizes the major histocombatibility complex (MHC-II) molecule. These "helper T-lymphocytes" cause the production of more cells for cell-mediate immunity, but they first must be activated by cytokines, such as interleukin I (Il-I).[2]
As well as being invoked by cytokines, they generate cytokines:
- Interleukin-2 (Il2)
- Interleukin-3 (Il3)
- Tumor necrosis factor alpha (TNFa)
- B-cell growth factor (BCGF)
- B-cell differentiation factor (BCDF)
T8 Killer cells
CD8-protein containing lymphocytes, also called T8-lymphocytes, are a subset of circulating "killer cells". All CD8-cells are killers, but other killer cells may be monocytes, macrophages (derived from monocytes) or polynuclear neutrophils. The key is that a killer cell attacks material labeled with the B-lymphocyte generated antibody.
These cytotoxic lymphocytes may be generated in vitro in mixed lymphocyte cultures (MLC), in vivo during a graft-versus-host (GVH) reaction, or after immunization with an allograft, tumor cell or virally transformed or chemically modified target cell. The lytic phenomenon is sometimes referred to as cell-mediated lympholysis (CML).
References
- ↑ NIH MeSH
- ↑ Kaiser, Gary E., T4 -Lymphocytes (T4-Cells; T4-Helper Cells; CD4+ Cells), "The adaptive immune system: I. Introduction, B. Major cells and key cell-surface molecules involved in adaptive immune responses", Doc Kaiser's Microbiology Home Page