12.2K: Tests That Differentiate Between T Cells and B cells
- Describe how T cells and B cells can be differentiated using staining of cell surface receptors and functional assays like the T lymphocyte cytotoxicity assay
Lymphocytes are the only immunologically specific cellular components of the immune system. They are divided into two types based on the pathogen recognition receptors they express on their surface. T cells or T lymphocytes belong to a group of white blood cells known as lymphocytes. They are called T cells because they mature in the thymus. They play a central role in cell-mediated immunity along with initiating rejection of foreign tissues following organ transplantation. B-cells are also white blood cells and are a vital part of the humoral immunity branch of the adaptive immune system. These two cell types can function independently or cooperatively to defend the body against pathogens. T-lymphocytes can be distinguished from other lymphocytes like B cells and natural killer cells (NK cells) by the presence of a T cell receptor (TCR) on the cell surface. Alternatively, B-cells can be distinguished from other lymphocytes like T cells and natural killer cells (NK cells) by the presence of a protein on the B-cell’s outer surface called a B-cell receptor (BCR).
Traditionally, T-lymphocytes were defined by their ability to form E-rosettes when they bind selectively to sheep erythrocytes. T-lymphocytes express CD3, CD4, CD8, or CD25 markers. B-lymphocytes express CD19 marker. The expression of different markers allows the separation/ differentiation of T and B cells. Another functional assay used to identify T-lymphocyte is the cytotoxic activity assay. This assay is based on measuring the killing ability that a determined number of T lymphocytes have for a certain number of target cells when both populations are placed together. B-lymphocytes have membrane-bound immunoglobulins that can be stained with anti-immunoglobulin labeled with fluorescent dyes and detected with a fluorescent microscope. More modern techniques like flow cytometry and immunohistochemistry are commonly used and rely on the use of fluorescent antibodies. These techniques are based on staining B and T cells for unique cell surface markers known as cluster of differentiation (CD).
Key Points
- There are two types of lymphocytes: B cells and T cells. These two components of the immune system have different functions but cooperate to fight infection.
- T cells elicit cell-mediated immune response, while B cells elicit humoral immunity.
- Lymphocytes are the only immunologically specific cellular components of the immune system.
Key Terms
- cytotoxic : of, relating to, or being a cytotoxin