Phytohämagglutinin

Phytohämagglutinin (PHA) is a type of lectin, a carbohydrate-binding protein, derived from plants. It is commonly used in immunology and cell biology research. PHA is extracted from various plant sources, including red kidney beans, lentils, and peas. The most widely used form is PHA-E, which is derived from the seeds of the red kidney bean (Phaseolus vulgaris). PHA-E is a tetramer, consisting of four identical subunits, each with a binding site for N-acetylgalactosamine (GalNAc), a sugar residue found on many cell surface glycoproteins.

PHA is used in various applications, including cell separation, cell adhesion studies, and as a mitogen to stimulate cell proliferation. It is particularly useful in the isolation of T cells from peripheral blood mononuclear cells (PBMCs) due to its specificity for GalNAc residues on T cell surfaces. PHA can also be used to study cell adhesion and signaling pathways by inducing cell aggregation and activation.

The mechanism of action of PHA involves its binding to GalNAc residues on the surface of target cells, leading to cell aggregation and activation. This process is mediated by the clustering of cell surface receptors, which triggers downstream signaling events. PHA is a valuable tool in immunology and cell biology research due to its specificity, ease of use, and ability to induce robust cellular responses. However, it is important to note that PHA can also induce non-specific effects, such as cell lysis and cytotoxicity, which should be considered when using this lectin in experimental settings.