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. The time interval between administration of the EEP and the immunization process should not exceed 48 hours.