In the present work the mechanism ofaction of Astragalus membranaceus was stu-died in tissue cultures

mice and human be-ings.Data obtained demonstrated that Astra-galus membranaceus had the capacity toprolong the life-span of some primary cellcultures and some diploid cell strains up to88-98 generations（374-465 days）.Some cellcultures

including human lung diploid cellcultures

treated with Astragalus membrana-ceus became resistant to cyto-pathogenic ef-fects caused by vesicular stomatitis virusand Sindbis virus.Results obtained also offe-red some evidences about the effect of As-tragalus membranaceus on the interferonsystem:1)stimulation of interferon induc-tion by virus inducer in mice;2)promo-tion of interferon-inducing ability of leuco-cytes from volunteers;3)inhibition of thecell RNA metabolism.Studies among volun-teers indicated that the nasal SIgA levelin patients suffering from recurrent commoncold after treatment with Astragalus mem-branaceus was markedly higher than thatbefore treatment and or that in untreatedpatients.It was shown that there was a pa-rallelism between the change of SIgA leveland the incidence of common cold.Studieson the isolation of active principles of As-tragalus membranaceus are under way.