Phytohemagglutinin-L (PHA-L) consists of only L-type subunits (isolectin L4, "leuko-agglutinin"), and is well suited for high-efficiency induction and the functional analysis of T-lymphocytes. It is highly purified and tested for high-efficiency stimulation of human lymphocytes. It is also used as positive controls for peripheral blood mononuclear cells (PBMC) stimulation.