A spontaneous lymphoma (141) producing monoclonal IgM is established in NZB/NZW F1 (B/W) mice who spontaneously develop an autoimmune disease. Idiotypic determinants of 141 IgM are present on the lymphoma cell surface as shown by indirect immunofluorescence and specific cytotoxicity with rabbit anti-idiotypic antiserum. Fluorescence and cytotoxicity are inhibited by 141 IgM but not by 104E IgM, a monoclonal IgM produced by a BALB/c plasmacytoma.
Immunization of B/W mice with 141 IgM before transplantation of lymphoma 141 confers protective immunity. No such protection occurs after immunization with 104E IgM or other unrelated proteins. Protected mice contain spleen cells cytotoxic for 141 lymphoma cells. This cytotoxicity is blocked by incubation of spleen cells with 141 IgM but not with 104E IgM. Moreover, splenic lymphocytes from protected mice are stimulated to synthesize DNA by 141 IgM but not by 104E IgM. These results suggest that specific cellular immune responses to idiotypic determinants may participate in the observed protection against challenge with the corresponding B-cell tumor.