Comparative study of different stinging nettle preparations regarding to their immunomodulating effect on primary human T-lymphocytes.

Urtica dioica L. (U. dioica) has shown anti-inflammatory effects and is regarded as a potential natural agent for treating chronic inflammatory conditions. The differential effects of U. dioica preparations have not yet been investigated. The influence of nine different U. dioica preparations (teas, extracts, juice and tincture) on proliferation, apoptosis/necrosis and viability of primary human T cells were analyzed with standard methods. The effect on T lymphocytes was evaluated via cluster of differentiation (CD)25/CD69 marker expression, degranulation assays and the production of pro-inflammatory cytokines. Using Jurkat reporter cell lines, an influence on transcription factors was analyzed. U. dioica preparations selectively modulate T cell activation by downregulating the key activation markers CD25 and CD69. In addition, they reduce the production of the pro-inflammatory cytokine interleukin-2, inhibit T cell degranulation and suppress nuclear factor of activated T-cells (NFAT)-dependent transcription. The results highlight the potential of U. dioica as a natural agent, capable to modulate T cell-mediated immune responses. The immunomodulating effect differs between the extracts and preparations due to extraction methods and used plant material.