## 4 Discussion  
The host immune system plays a crucial role in defending or inhibiting several pathological conditions, such as infections and tumors [18; 19]. however, the most important aspect of the immunity is the balance between activation and inhibition. There are some plant extracts or their components that have been reported to have an immunostimulant effects under normal conditions, whereas they have an immunosuppressive effect in inflammatory environments, such as LPS treatment [7; 20; 21; 22]. In the present study, we have revealed the immune-enhancing effect of RPGE. RPGE-C or RPGE-P treatment significantly increased phagocytic activity in macrophages, as well as NO production and mRNA expression levels of innate immune-related cytokines. Moreover, our previous studies have also confirmed the mitigating effects of RPGE on the LPS-induced inflammatory response in splenocytes isolated from mice [8]. Therefore, we concluded that RPGE has immunomodulatory properties in immune cells. NF-kB and MAPK signaling play a crucial role in immune responses [1; 4; 23; 24]. however, the relationship between the two signaling pathways remains unclear. here, our results show that RPGE stimulates the immune responses in RAW 264.7 cells via two different mechanisms. RPGE has shown to increase phosphorylation levels of NF-kB, as well as increase p38 MAPK-induced NF-kB activation. The inhibition of NF-kB and p38 reduced RPGE-induced macrophage activation (Figure S1). Therefore, our results suggest that RPGE is a promising functional food for enhancing immunity. Moreover, further studies on the immunomodulatory effect of RPGE may further understanding of the molecular mechanisms underlying the immune response. The functional food industry has used various processing methods to increase the active ingredients of raw materials [25; 26; 27]. Approximately 30 different active ingredients of PG are known [28], including  
Figure 8: Effect of RPGE on cell viability and secretion of IL-10 in mouse splenocytes. (**a**) Mouse splenocytes were incubated with Con A (5 ug/mL), LPS (1 ug/mL), or various concentrations of RPGE-C; (**c**) Mouse splenocytes were incubated with Con A (5 ug/mL), LPS (1 ug/mL), or various concentrations of RPGE-P. Con A, Concanavalin A; LPS, lipopolysaccharide. The results were expressed as a relative value to that of VC, which is set to 100%. The data are represented as the mean \(\pm\) SEM. **\(p<0.01\) and ***\(p<0.001\) as when compared with the VC. (**b**) IL-10 protein level (RPGE-C); (**d**) IL-10 protein level (RPGE-P). All data are represented as the mean \(\pm\) SEM. *\(p<0.05\) and ***\(p<0.001\) as when compared with the VC. platycodin D, the representative saponin in PG (Figure S2A). In this study, we steamed and dried raw PG several times, thereby increasing the content of platycodin D by approximately three times when compared to white PG (Figure S2B). This process is similar to the increase in the saponin content of red ginseng compared to white ginseng [5; 26; 27]. Moreover, this increase in the content of active ingredients may further improve the functionality of PG. To determine the cellular mechanism of the immune-enhancing effect of RPGE, we used the murine macrophage cell line, RAW 264.7. The viable cell population was increased by RPGE treatment (Figure 1a,b). The mean proliferation rates after treatment with the highest concentration of RPGE-C and RPGE-P (500 ug/mL) were increased by approximately 60% and 50% compared to the VC, respectively. Thus, our results demonstrate that RPGEs induce macrophage cell proliferation in RAW 264.7 cells. Interestingly, extracellular-signal-regulated kinase (ERK) activity was increased in cells treated with RPGE-C (Figure S3A) or RPGE-P (Figure S3B). ERK is a family of MAPK that plays a role in regulating cell growth signals [29; 30]. When cells were cotreated with RPGEs and an ERK inhibitor (PD98059), NF-kB activity was increased (Figure S3C).