The polysaccharide of (PAMK) alleviates cyclophosphamide-mediated immunosuppression in geese, possibly through novel_mir2 targeting of CTLA4 to upregulate the TCR-NFAT pathway.

The polysaccharide of (PAMK) has been proved to have antioxidant, anti-inflammatory, antiviral, and immunity promoting effects. MicroRNAs (miRNAs) have also been shown to participate in the regulation of immune function by negatively regulating the expression of target genes. However, little is known about how PAMK alleviates the immunosuppression the miRNA pathway in geese. The aim of this study is to evaluate the influence of PAMK on immunosuppression. Magang geese (1 day old, = 200) were randomly divided into groups, namely, the control group (normal feeding), PAMK (fed 400 mg kg PAMK), CTX (injected 40 mg kg BW cyclophosphamide), and CTX + PAMK (40 mg kg BW cyclophosphamide + 400 mg kg PAMK) groups. Thymus development was examined by the thymus index, transmission electron microscopy and scanning electron microscopy. The T cell proliferation rate was stimulated by phytoagglutinin (PHA), and T cell activation related genes (CD28, CD96, MHC-II), and IL-2 levels in serum were detected. Differentially expressed miRNAs of geese to regulate T cell activation were found by miRNA sequencing technologies. The results showed that PAMK could alleviate thymus damage and the decrease in the T lymphocyte proliferation rate, T cell activation, and IL-2 levels that were induced by CTX. MiRNA sequencing found that the combination of PAMK and CTX significantly promoted T cell activation upregulation of novel_mir2 ( < 0.05), which inhibited cytotoxic T lymphocyte antigen 4 (CTLA4) expressions, thereby promoting the TCR-NFAT signaling pathway. It can be concluded that PAMK, through novel_mir2 targeting of CTLA4 to upregulate TCR pathway, finally alleviated immunosuppression induced by CTX in geese.