Objective: We recently reported that OMC-2010 has an immuno-modulatory effects via inhibiting tumor necrosis factor (TNF)-α and interleukin (IL)-5. However, we did not find out which constituents play an important role in immuno-modulatory effect of OMC-2010, Thus, this study was performed to estimate the effects of constituents of OMC-2010 on cytokine production in mouse spleen cells, then ultimately reach to find out effective constituents regulating splenic cytokine production. Methods: Mouse spleen cells were pre-treated with water and ethanol extract of constituents of OMC-2010 such as Rehmannia glutinosa (RG), Pinellia ternata (PT), Citrus unshiu Markovich (CUM), Glycyrrhiza uralensis (GU), Platycodon grandiflorum (PG), Schisandra chinensis (SC). After 1 h, the cells were stimulated with lipopolysaccharide (LPS, 1 ㎍/ml) for 48 h. Then the cells were harvested for real-time reverse transcription polymerase chain reaction to detect cytokine productions. Results: The water extract of RG extract significantly inhibited the LPS-induced inTNF-α and IL-5 mRNA expressions, but the water extract of PT, CUM, GU, PG, and SC did not. The ethanol extract of RG, PT, and SC significantly inhibited the LPS-induced TNF-α, and IL-5 mRNA expressions, but the ethanol extract of CUM, GU, and PG did not. Conclusions: Theses results could suggest that the water extract of RG and the ethanol extract of RG, PT, and SC inhibited the expression of TNF-α and IL-5, which means that the possible candidate of OMC-2010 water extract`s action might be RG, and ethanol extract`s action might be RG, PR, and SC.