Objective: Stinging nettle leaf extracts are registered in Germany for adjuvant therapy of rheumatic diseases. In a whole blood culture system the nettle extract IDS 23 (Rheuma-Hek) inhibited lipopolysaccharide stimulated monocyte cytokine expression, indicating an immunomodulating effect. We investigated the immunomodulating effects of IDS 23 on phytohemagglutinin (PHA) stimulated peripheral blood mononuclear cells (PBMC) in vitro.
Methods: Using commercial immunoassays the distinct cytokine patterns of Th1 and Th2 cells were determined. Interleukin 2 (IL-2) and interferon-gamma (IFN-gamma) mRNA expression was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) with PHA stimulated PBMC.
Results: IDS 23 inhibited PHA stimulated production of Th1-specific IL-2 and IFN-gamma in PBMC culture (n = 10) in a dose dependent manner up to 50+/-32% and 77+/-14%, respectively. In contrast, IDS 23 stimulated the secretion of Th2-specific IL-4. The dose dependent inhibiting effect on IL-2 and IFN-gamma expression was also detected with RT-PCR, while the amount of actin-specific mRNA transcript was not modified by IDS 23.
Conclusion: Our results suggest the effective ingredient of IDS 23 acts by mediating a switch in T helper cell derived cytokine patterns. IDS 23 may inhibit the inflammatory cascade in autoimmune diseases like rheumatoid arthritis.