An extract of the fern Polypodium leucotomos inhibits human peripheral blood mononuclear cells proliferation in vitro

Abstract

An alcoholic extract of the fern Polypodium leucotomos (PLE) has been empirically used as an immunosuppressor for the treatment of several autoimmune diseases. In this paper, we investigated the effects of PLE on activation and proliferative responses of peripheral blood mononuclear cells (PBMNC) from healthy donors to T lymphocyte polyclonal mitogens. PLE shows a significant inhibitory effect on the proliferative response of PBMNC to stimulation with phytohaemagglutinin (PHA) or anti CD3 monoclonal antibodies ( P < 0.05). In contrast, PLE did not modify the proliferative response of PBMNC to phorbol esters ( P > 0.05). The inhibitory effect of PLE upon mitogen induced PBMNC proliferation is time dependent and can be overcome by the exogenous addition of interleukin-2 to the culture medium ( P < 0.05). The decreased proliferative response of PBMNC to PHA stimulation in the presence of PLE is not associated with a significant modification of expression of the α chain (CD25) of the IL-2 receptor ( P > 0.05). In conclusion, PLE shows an inhibitory effect on the polyclonal proliferative response of PBMNC to T lymphocyte mitogens that interact with cytoplasmic membrane molecules.