Medicinal plants have been used for centuries and have become part of complementary medicine worldwide because of their potential health benefits. Some of their metabolites have been successfully used directly in the treatment and prevention of infectious diseases and cancer, or indirectly by stimulating the immune system. In the present study, we investigated the effects of methanol and aqueous extracts of the Mexican plants Ocinum basilicum, Persea americana, Plantago virginica, and Rosa spp. on in vitro rat lymphocyte proliferation. Methanol extracts of O. basilicum, P. americana, P. virginica, and Rosa spp.stimulated up to 80, 16, 69 and 66%  lymphoproliferation, respectively, whereas their respective aqueous extracts induced up to 83, 48, 31 and 83% lymphoproliferation, as compared with untreated controls. The effect of O. basilicum aqueous extract at concentrations of 31.25, 62.5, 125 and 250 g/ml on lymphoproliferation was significantly different (p < 0.05) than the effects of P.americana and P. virginica at the same concentrations. We also observed that the lymphoproliferative effect of Rosa spp.  aqueous extract was significantly higher (p < 0.05) than that of the methanol extract. Methanol and aqueous vehicles did not affect lymphocyte viability nor proliferation activity. The observed immunostimulatory effect may be of benefit in increasing the pool of lymphocytes in immunodeficiency patients.

Key words: Ocimum basilicum, Persea americana, Plantago virginica, Rosa spp., immunoregulation, lymphocyte proliferation, phytomitogens, mexican plants