Immunosuppressive effect of a low molecular weight surface protein fromRenibacterium salmoninarumon lymphocytes from Atlantic salmon (Salmo salarL.)

The immunosuppressive effect ofRenibacterium salmoninarumsurface proteins, p22 and p57, on lymphocytes was studied. It has been shown earlier that the p57 protein suppresses the antibody production by salmonid B cells. In this study, the suppressive effect of a surface protein with a molecular weight of 22 kDa was compared with that of p57. The p22 and p57 proteins were isolated by gel filtration. The purity of the proteins was assessed by SDS–PAGE and Western blotting using a monoclonal antibody to p57 and a mouse antiserum to p22. Both p22 and p57 were found to suppress the specific antibody production by salmonid B cellsin vitro, as measured by ELISPOT. The proteins also agglutinated salmon leucocytes.