The A beta 6w302 gene and molecular mechanisms of resistance to the spread of radiation-induced lymphoma in a mouse mutant, survivor-27.

Metastatic tumors escape from immune response and spread in the body; survivors are very rare. Novel single exon genes A beta 4-7 and a pseudogene A beta 8 psi have been cloned from survivors. Their protein coding sequences are similar to MHC class II beta H2-Ab cDNA while their promoter is different from MHC promoters. The A beta 4 protein was demonstrated on macrophages (antigen presenting cells). The A beta gene family is genetically unstable in germ line and somatic cells of survivors. Mutants S-27 and S-87/1 lost the A beta 5s5 and acquired the A beta 6w302 gene; the Ab gene mutated in S-27. The proposed mechanism of resistance is molecular instability of the A beta gene family resulting in somatic mutations and wandering immune responses that destroy the tumor in the survivor.