Effects of Astragalus polysaccharides (APS) on the expression of immune response genes in head kidney, gill and spleen of the common carp, Cyprinus carpio L.
For fish immune defences, cytokines and anti-microbial peptides (lysozyme) in circulating system play important roles.  In the present study, the effects of Astragalus polysaccharides (APS) injection on gene expression of interleukin 1beta (IL-1beta), tumor necrosis factoralpha (TNF-alpha) and lysozyme-C in the head kidney, gill and spleen of common carp were determined using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR).  After injection of APS, IL-1beta mRNA level increased in a dose-dependent manner in the head kidney, while no significant changes were found in the gill and spleen.  High dose of APS up regulated TNF-alpha transcription in the gill and spleen, while TNF-alpha mRNA level decreased significantly in the head kidney of low dose of APS.  Lysozyme-C mRNA levels were up regulated in the gill of low dose of APS and spleen of middle dose of APS.  No effect of the APS on lysozyme-C expression was observed in head kidney.  These results constitute a first step toward the understanding of APS effect on cytokines and immune-related gene expression in different organs of common carp.