Lymphocyte

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This editable Main Article is under development and subject to a disclaimer.

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## Contents

* 1 B-lymphocyte
* 2 T-lymphocyte
* 2.1 T4 Helper Cells
* 2.2 T8 Killer cells
* 3 References

A lymphocyte is a type of leukocyte (i.e., white blood cell), which are a major component of the immune system. The group broadly breaks into B-lymphocytes and T-lymphocytes. [1]

The lymphocyte count is "the number of lymphocytes per unit volume of blood."[2]

## B-lymphocyte[edit]

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[edit]

Lymphocytes of these types directly destroy appropriate target cells, or help generate cells that do.

### T4 Helper Cells[edit]

T-lymphocytes with the T4 protein on their surface which recognizes the antigenic peptide while the CD4 molecule recognizes the major histocompatibility complex (MHC-II) molecule. These "helper T-lymphocytes" cause the production of more cells for cell-mediated immunity, but they first must be activated by cytokines, such as interleukin-1 (Il-I).[3]

As well as being invoked by cytokines, they generate cytokines:

* Interleukin-2 (Il2)
* Interleukin-3
* Tumor necrosis factor-alpha (TNFa)
* B-cell growth factor (BCGF)
* B-cell differentiation factor (BCDF)

### T8 Killer cells[edit]

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 transplantation#allograft, tumor cell or virally transformed or chemically modified target cell. The manner in which these cells destroy targets is sometimes called cell-mediated lympholysis (CML).

## References[edit]

1. ↑ Anonymous (2026), Lymphocyte (English). Medical Subject Headings. U.S. National Library of Medicine.
2. ↑ Anonymous (2026), Lymphocyte count (English). Medical Subject Headings. U.S. National Library of Medicine.
3. ↑ 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