Expression of normal histocompatibility antigens in murine lymphomas treated with 5-(3,3′-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) in vivo

Novel transplantation antigens have been detected in a Moloney virus-induced LSTRA lymphoma of BALB/c origin (H-2^d), or in a chemically-induced L5178Y lymphoma of DBA/2 origin, following treatment of tumor-bearing hosts with 5-(3,3′-dimethyl-1-triazeno-)-imidazole-4-carboxamide (DTIC), for 4–8 transplant generations. Marked cell-mediated cytotoxic responses against DTIC-treated LSTRA or L5178Y lines were found by primary in vivo and secondary in vitro sensitization of histocompatible mice. Moreover, preliminary data show that no obvious antigenic cross-reactivity can be found among DTIC-treated sublines derived from distinct parental lymphomas. To test whether DTIC lines would express variable levels of normal histocompatibility antigens, cytotoxic lymphocytes were generated in vitro against alloantigens of H-2 complex or sub-regions of it and tested against parental or DTIC-treated lymphomas in a short-term ⁵¹Cr-release assay. A cold-inhibition test was performed with LSTRA or 4 LSTRA/DTIC sublines. The results showed that little or no difference in the expression of H-2 antigens recognized by cytotoxic lymphocytes could be detected between parental and DTIC-treated sublines. Moreover, no foreign H-2 specificities of H-2^b or H-2^k haplotypes detectable by cytotoxic lymphocytes could have been found in L5178Y or L5178Y/DTIC lymphomas.