Thirteen of the immune-related genes were confirmed with RT–qPCR and six of those cytokines were further confirmed by western blot. The differential expression of a range of immunerelated genes in the porcine thymuses suggests that the infection pressure of PCMV affects the immune process of the host. The results of GO annotation and KEGG analyses showed that several of the differentially expressed genes are involved in cellular signaling pathways, including the genes for T-cell receptor, TLR, NF-kB, B-cell receptor, TNF, p53, and TGF-b, and others are involved in the cytokine–cytokine receptor interaction signaling pathways. TCR signaling in response to antigen recognition plays a crucial role in the adaptive immune response. In this study, the expression levels of most genes involved in the TCR signaling pathway were downregulated, including those encoding cytotoxic T-lymphocyte-associated protein 4, CD4/8, lymphocytespecific protein tyrosine kinase, CD3e, CD3d, E3 ubiquitin protein ligase, CD40 ligand, NF-kB, IL-2, TNF-a, inducible T-cell co-stimulator, growth factor receptor-bound protein 2, and pyruvate dehydrogenase kinase isozyme 1. This suggests that the TCR signaling pathway is significantly inhibited during infection by PCMV. TGF-b is an immunosuppressive cytokine, and it plays an important regulatory role in several cellular processes and immune functions. The TGF-b signaling pathway is also involved in apoptosis, cell differentiation, and growth. Recent research has shown that the proliferation of activated T cells is suppressed by apoptosis and the release of TGF-b1 during HCMV infection. Human immunodeficiency virus and hepatitis C virus infections also activate the TGF-b signaling pathway. In the present study, the results of a GO annotation analysis showed that several of the upregulated genes are associated with the TGFb signaling pathway, including genes encoding TGF-b2, TGF-b3, inhibitors of DNA binding 1/2/4, activin RI, decorin, and inhibin bB. This suggests that the activated TGF-b signaling pathway may function in PCMV infection as it does during infections by other immunosuppressive viruses. The interferons are Epoxomicin proteins with antiviral and immunoregulatory activities, and they have been shown to play essential roles in the host responses to viruses of the family Herpesviridae. An HCMV-derived IL-10 homolog was shown to suppress the TLR-induced expression of IFN-a/b genes in infected plasmacytoid dendritic cells, thus inhibiting the antiviral and immunoregulatory activities of the host. However, in the present study, the expression of the genes encoding IFN-a/b were not significantly upregulated in porcine thymuses after PCMV infection. The TLR family is the first line of defense against infectious agents, and it plays a fundamental role in the innate immune response. These proteins identify and monitor pathogen-associated molecular patterns and also mediate the expression of the cytokines that are necessary for immunity. Currently, roles for TLRs in infections by members of the family Herpesviridae have been reported.