Phytohemagglutinin

The phytohaemagglutinin (known as PHA for the abbreviation of Phytohaemagglutinin) is a lectin widely distributed among legumes and in some oilseeds including Glycine max soybean.

Lectins are proteins that recognize carbohydrates and are characterized by their ability to combine with gram + membrane receptors.

Structurally, they are formed by a lectin-like domain and a globular domain that is the one that recognizes carbohydrates. PHA was recognized for its ability to agglutinate erythrocytes and leukocytes. In addition, it non-specifically stimulates the proliferation of both B and T cells, it is this mitogenic characteristic that gives it its main application. It is used in the protocol for preparing cells in culture to perform karyotyping to detect possible chromosomal abnormalities. The cells are incubated with this lectin which induces their mitosis and proliferation. Once a large part of the chromosomes is considered to be in metaphase, colchicine is added, which is an agent that stops the cycle in metaphase, a necessary state to perform the karyotype. Once the cells are arrested in metaphase, an osmotic shock occurs so that they swell and be able to fix their nuclei for the study of chromosomes. Now that they are fixed on a slide, they are stained. Recent studies with rats fed with purified lectins isolated from red bean Phaseolus vulgaris seed have shown direct lectin binding to the intestinal mucosa (Almeida et al. 1991; Santiago et al. 1993), interacting directly with enterocytes and interfering with the absorption and transport of nutrients (i.e. carbohydrates) during digestion (Santiago et al. 1993) and causing epithelial lesions in the intestine (Oliveira et al. 1989).