The
fibrosarcoma ST2, induced by
3-methylcholanthrene in BALB/c (H-2d) mice, also expressed alien
histocompatibility antigens of the C3Hf and B10 background not encoded by the MHC. To examine the relationship between these alien, minor
antigens and the
tumor-specific transplantation antigen (
TSTA) of the
tumor, in vivo immunogenicity test were performed in BALB/c mice and in hybrids between BALB/c and C3Hf (H-2k), C3H.
OH (H-2o2), C3H.SW (H-2b), BALB.K (H-2k), B10.BR (H-2k), and B10.D2 (H-2d) mice. A significant loss of
TSTA immunogenicity was found in (BALB/c x C3Hf) and in (BALB/c x C3H.
OH)F1 animals and, to a lesser extent, in (BALB/c x C3H.SW)F1 mice as compared to the immunogenicity of the
tumor in BALB/c mice. Immunogenicity tests with ST2 in BALB/c x (BALB/c x C3Hf) or in BALB/c x (BALB/c x B10.D2) backcross mice, respectively, revealed that half of the BALB/c x (BALB/c x C3Hf) and 97% of the BALB/c x (BALB/c x B10.D2) animals were able to mount an immune response to ST2. To see whether the loss of
TSTA immunogenicity in (BALB/c x C3Hf) was due to common determinants shared between
TSTA and alien non-H-2 C3Hf
antigens or to a genetically linked low responsiveness to
TSTA introduced by C3Hf and C3H.
OH strains, BALB/c mice were immunized with normal tissues of some BALB/c x (BALB/c x C3Hf) backcross, anti-ST2 resistant mice. Normal tissues of anti-ST2 resistant, dd and dk typed backcrosses were able to immunize BALB/c mice against a challenge of an otherwise lethal dose of ST2 cells. Some but not all BALB/c x (BALB/c x B10.D2) anti-ST2 resistant donors had tissues able to immunize BALB/c hosts aginst the ST2 growth. Since resistance to
tumor growth and expression of minor "alien"
antigens shared with the
tumor segregate independently, we concluded that alien, minor C3Hf and B10
antigens of the BALB/c
sarcoma ST2 are distinct from the
TSTA of this
tumor.