Thymoquinone, the primary bioactive compound of Nigella sativa (black seed), has been investigated for its potential effects on autoimmune disorders in preclinical studies. Scientific interest stems from its documented anti-inflammatory, antioxidant, and immunomodulatory properties. Several in vitro and animal studies have shown that thymoquinone can modulate immune cell activity, reduce production of pro-inflammatory cytokines (such as TNF-α and IL-6), and suppress oxidative stress, which are relevant mechanisms in the context of autoimmune diseases.

For example, preclinical models of autoimmune conditions such as rheumatoid arthritis, multiple sclerosis, and type 1 diabetes have demonstrated that thymoquinone administration can reduce disease severity, decrease inflammatory infiltrates, and modulate immune responses. However, these findings are limited to animal and cell culture studies; robust human clinical trials are lacking. There are a few small pilot studies or case reports involving Nigella sativa (the seed or oil) in autoimmune contexts, but these do not isolate thymoquinone as the active agent or provide high-quality evidence.

In summary, while there is a scientific rationale supported by mechanistic and preclinical evidence, there is insufficient clinical validation in humans. Therefore, the evidence is rated as modest (2/5), reflecting potential but unconfirmed benefit pending further research.