Porcine circovirus type 2(PCV2)mainly damages the immune cells of pigs,causing lym-phocyte depletion and immune suppression.Interleukin(IL)-15 regulates immune functions wide-ly,and plays an important regulatory role in the survival,proliferation,differentiation and immune function of a variety of immune cells such as natural killer(NK),CD8+T cells and NKT cells.In this study,in order to determine the effect of PCV2 on IL-15 expression,4-week-old piglets(n=4)were infected with PCV2 and the negative control group(n=4)was set up.On day 7 post-infec-tion,the inguinal lymph nodes of the infected and control groups were collected,and porcine cyto-kine antibody microarray(QAP-CYT-1)was employed to quantify the expression of cytokines in the tissues,screen for differential cytokines,and GO and KEGG enrichment analysis for IL-15 were conducted.Real-time quantitative fluorescent PCR(qPCR)and ELISA were used to verify the level of IL-15 mRNA and protein,and those in porcine peripheral blood mononuclear cells(PBMC)and serum were simultaneously detected.Compared with the negative control group,the expression lev-el of IL-15 was significantly reduced in the infected group(P＜0.05);IL-15 was mainly involved in cytokine-cytokine receptor interactions,immune responses,cellular activation,and the regulation of JAK-STAT and TNF signaling pathways.The levels of IL-15 mRNA and protein in inguinal lymph nodes in the infected group were significantly lower than those in the control group(P＜0.05),which was consistent with the detection results of QAP-CYT-1.However,there was no significant difference in IL-15 mRNA and protein levels in PBMC and serum.These results indicate that PCV2 can inhibit IL-15 in the inguinal lymph node microenvironment of piglets.This study can provide important information for further revealing the immunosuppressive mechanism of PCV2.