We assessed the effects of C. nervosum , G.pentaphyllum, H. suaveolens and P. grandiflora on NK cell activity, one of natural defense Our studies demonstrated that the extracts of C. nervosum and H. suaveolens stimulated NK cell activity. Different immunomodulating profiles may provide a rational basis and support for plant selection aimed at drug discovery. Our data revealed that those plant extracts show promising lymphocyte stimulating activities on non-specific cell-mediated immune responses. Purification of active components may be required for potential and clinical applications as immunomodulators.