IN many hypotheses concerning the mechanism of the immune response the nucleic acids have been assigned a role in the production of antibodies, although no clear evidence for their participation is yet available. As regards protein synthesis in general, there is reason for believing that the ribonucleoproteins lie in the pathway of this synthetic process1. Evidence also exists that certain enzymes are present in the ribonucleoprotein complex2,3, and it is possible that they represent products of protein synthesis mediated by ribonucleoprotein. The present communication describes an attempt to ascertain whether antibodies also are present in ribonucleoprotein complexes isolated from the antibody-forming organs, spleen and lymph nodes, of the rabbit.