Griffonia simplicifolia lectin (GSL I+II) is isolated from a woody climbing shrub native to Africa. It consists of both lectins GSL I+II, that a molecular weight of 114,000 and an isoelectric point between pH 5.0 to pH 6.5. This lectin has carbohydrate specificity for betaGal and GalNAc, and elutes with galactose or N-acetylgalactosamine. GSL I+II shows specificity for blood group B greater than blood group A1.

This lectin interacts with pulmonary microvascular endothelial cells, but does not readily interact with pulmonary arterial endothelial cells. This binding pattern has been successfully utilized to enrich cell populations in vitro that possess functional behaviors characteristic of those seen in vivo.