Phytohemagglutinin (PHA) stimulates the transformation of peripheral blood lymphocytes into lymphoblasts, restoring their proliferative potential. This enables the dividing cells to be used for chromosomal karyotyping, while further driving lymphoblast proliferation and subsequent release of lymphokines.

Phytohemagglutinin-M (PHA-M) is a compound extracted from the herbaceous angiosperm Phaseolus vulgaris (red kidney bean). As a non-immunogenic protein/glycoprotein, it specifically recognizes carbohydrates. By altering the physiological properties of cell membranes, PHA-M modulates protein permeability, disrupts cellular metabolism, and thereby induces mitosis or other cellular biochemical responses.