Sutherlandia frutescens
(SF) is one of the medicinal plants used as an immune booster in the treatment of chronic
ailments such as HIV/AIDS and cancer. Limited data suggest that its efficacy is based on its regulatory effect on cytokines,
the critical components of the immune response. In this study, we investigated the
in vitro immunomodulatory effects of SF
extracts on normal human peripheral blood mononuclear cells (PBMCs). An ELISA-based assay was used to assess the levels
of expression of 12 cytokines in treated cells. An adenosine triphosphate (ATP) assay was used to assess cell viability in
relation to cytokine secretion. SF ethanol extracts induced changes in cytokine secretion relative to the dose of the extract.
Generally cytokine expression and secretion was low in concentration because were not stimulated with any endotoxin. The
high SFE dose (2.5 mg/ml) significantly (
p<0.001) decreased some cytokines including TNF-α and IL 1β. Low doses of this
extract (0.5 mg/ml) did not change TNF-α and IL 1β secretion from the baseline (untreated cells). Changes in cytokine
secretion of SFE treated cells tracked changes in ATP levels (cell viability). The SFW extract-induced changes in cytokine
secretion were independent of cell viability. TNF-α was decreased (
p<0.001) by the high dose of SFW extract while IL 1β
and IFNγ were increased (
p<0.01) by the same dose. High doses decreased cell viability which was reflected in cytokine
secretion. It is evident, from these results, that SF extracts can modulate cytokine secretion in unstimulated normal PBMCs
in
vitro. Further studies in animal models are recommended to advance understanding of this immunomodulatory activity.
