Studies on a new lymphocyte mitogen from pollen aqueous extract: induction of proliferation in human and rodent...

Fraction III (Fr III) mitogen was isolated from the whole aqueous extract (WAE) of plane-tree pollen by Con A-Sepharose chromatography and gel filtration. It stimulated mouse spleen cells, and peripheral blood lymphocytes from plane-tree non-sensitive patients or from cord blood. A 6-day culture gave the best response. The proliferation was not abolished by washing the cells after a short pulse of Fr III given in the initial step but was inhibited by alpha-D-methylmannoside. These results suggested that Fr III bound to a specific site onto spleen cells. This mitogen was not immunogenic in mice and did not bind to human IgE. It induced the proliferation of T lymphocytes in presence of accessory cells and was a polyclonal activator.