## 4 Discussion
In comparison-I, 150 DEGs were enriched in immune-system processes in the biological function category (Table S1a) which can be candidate genes in the immune-modulation effect of PGE. Similarly, 82 DEGs were enriched in defense/immunity protein (PC00090) in the protein-class category (Table S4b). In pathway enrichment analysis 70, 26, 21, 18, 12, 4 DEGs were found to be from inflammation mediated by the chemokine-and-cytokine signaling pathway (P00031), B cell activation (P00010), T cell activation (P00053), the interleukin signaling pathway (P00036), the toll receptor signaling pathway (P00054), and the interferon-gamma signaling pathway (P00035), respectively (Table S5b). All of these enriched immune-system-related pathways directly modulate the immune function and response [35; 36]. Similarly, in comparison-II the functional enrichment 51 DEGs were enriched in immune-system processes in the biological-function category (Table S1b). In addition, 29 DEGs were enriched in defense/immunity protein (PC00090) in the protein-class category (Table S4b). In pathway-enrichment analysis 33, 13, 9, 5, 4, 2 DEGs were found to be from inflammation mediated by the chemokine-and-cytokine signaling pathway (P00031), B cell activation (P00010), T cell activation (P00053), toll-receptor signaling pathway (P00054), interleukin-signaling pathway (P00036) and interferon-gamma signaling pathway (P00035), respectively (Table S5b). Molecular function of these candidate DEGs can be studied in future studies, which may unveil their precise role in immune enhancement [35; 36]. To further explore the role of DEGs in context to immune modulation, two gene sets, i.e., gene set-1 and set-2 were created and used in set analysis. Gene set-1 was composed of immunity genes present in IMGT/GENE-DB [29] that are involved in immune function, and gene set-2 comprised genes that suppress the immune function [30]. In set analysis, it was found that no genes were down-regulated from gene set-1 in both the comparisons. However, 61 and 8 genes were found to be up-regulated in comparison-I and comparison-II, respectively, which was consistent with the immune-enhancement properties PGE observed in different studies [5; 6]. These genes were mostly composed of immunoglobulin genes that directly act as receptors in immune response [29]. These immunoglobulins were also found to be up-regulated in earlier studies carried out to study immune enhancement in PGE treatments [5; 6; 7]. Similarly, when gene set-2 was used in set analysis, a high number of immune suppressive genes were found to be down-regulated compared to up-regulated genes in both the comparisons (Figures 4 and 5). The mechanism that down-regulates immune-suppressive genes is expected to increase immunity-related function and immune enhancement [30]. Therefore, a higher number of down-regulated immune-suppressive genes again justifies the immune-enhancing effect of PGE treatment [30]. All (125) down-regulated immune-suppressive genes in comparison I were also found to be down-regulated in comparison II. Expression of immunosuppressive genes can be used to study immune modulation in future high-throughput studies as the current finding is in line with the immune-enhancement effect of PGE. Furthermore, the protein-protein interaction (PPI) analysis was carried out in addition to the function enrichment and pathway analysis for common down-regulated immune-suppressor genes. The protein-protein interaction network of these common down-regulated immune-suppressor genes resulted in a highly connected network compared to random possible connections (Figure 6), which suggests that there must be some pattern in expression of genes in our study that may be attributed to the PGE treatment and immune-suppressive nature of the genes. Furthermore, KEGG enrichment analysis through the STRING PPI server revealed that three cancer-related pathways were associated with 16 immune-suppressive genes (Table S7) [32;33].