Comparative delineation of T cell clonotypes in coexisting syngeneic B16 melanoma

B16 is a murine melanoma of C57Bl/6 origin, which rapidly develops as a tum or when inoculated into syngeneic immunocompetent hosts. Nevertheless, B16 tumors are considered to be immunogenic since tumor regression can be induc ed by means of immunotherapeutic intervention. Furthermore, B16 melanoma ce lls express several melanoma-associated antigens that may serve as targets for autologous T cells. To study the in vivo T cell response against B16, w ith particular emphasis on diversity and systemic involvement, we examined the spectra of T cell clonotypes in coexisting B16 melanoma lesions in C57B l/6 mice. Three tumors from each animal (n = 8) were examined for the prese nce of clonotypic T cells using the highly sensitive T cell receptor (TCR) clonotype mapping technology. Systematic analysis of the TCRB variable regi ons 1-16 revealed from 19 to more than 30 clonotypic TCR transcripts in eac h tumor. To study intra- and inter-individual variations in the T cell resp onse further, more than 600 clono-typic TCR transcripts were compared for s equence identity. Overall, approximately 2% of the T cell clonotypes were d etected in more than one tumor from the same animal. Furthermore, none of t he detected clonotypes was present in more than one animal, arguing against recurrent or "public" T cell responses against B16 melanoma. Our data stro ngly suggest that anti-melanoma T cell responses in this murine model encom pass mainly localized T cells, and that systemic involvement is limited.