The ability of ethanol extract of propolis to stimulate plaque formation in immunized mouse spleen cells.

Ethanolic extract of propolis (EEP) is capable of increasing the number of plaque-forming cells in spleen cell population of immunized male BALB/c mice, demonstrating their ability to produce antibodies. The single EEP dose exerting the maximal plaque formation (a three-fold increase over control) is 500 micrograms/mouse. When this dose is repeated within 24 hours--the plaque-producing effect is even stronger, but further increases in the propolis dose or in the number of its administrations, have an inhibitory effect on the formation of the plaques.