The influence of Nigella sativa essential oil on proliferation, activation, and apoptosis of human T lymphocytes in vitro

In previous work, we tested the immunomodulatory effect of Nigella sativa (NS) fatty oil. Our results demon-strated that unrefined, obtained by cold pressing black cumin seed oil inhibited lymphocytes' proliferation and induced their apoptosis in a dose-dependent manner. In this study, we examined the immunomodulatory properties of essential oil (EO) obtained from the NS seeds by hydrodistillation and its two main constituents: thymoquinone (TQ) and p-cymene. We analyzed the proliferation, activation phenotype, and apoptosis rates of human T lymphocytes stimulated with an immobilized monoclonal anti-CD3 antibody in the presence of serial ethanol dilutions of tested oil or serial distilled water dilutions of tested compounds with flow cytometry. Our results showed that NSEO significantly inhibited the proliferation of CD4(+) and CD8(+ )T lymphocytes, induced cell death in a dose-dependent manner, and reduced the expression of CD28 and CD25 antigens essential for lymphocyte activation. TQ inhibited the proliferation of T lymphocytes and induced cell death, particularly in high concentrations. Meanwhile, p-cymene did not influence lymphocyte proliferation. However, its high con-centration induced cell necrosis. These results show that the essential oil from Nigella sativa has powerful immunomodulatory properties, which, at least partially, are related to the TQ component.