AKR mice are highly susceptible to development of spontaneous T-cell lymphoma. Thymus removal at the age of 1–3 months greatly reduces T-cell lymphoma. Lymphomas that have the characteristics of T- and/or B-cells occur sporadically in peripheral lymphoid tissues of old thymectomized AKR/J mice. These thymectomized mice were shown to carry dormant potential lymphoma cells. Transplantation of lymphoid cells from 8–12-month-old AKR/J mice, thymectomized at the age of 6 to 8 weeks, into intact or thymectomized young recipients yielded 80–100% Ly-1+ pre-B or B-cell lymphomas. In the AKR-Fv-1b congenic strain the Fv-1n allele of AKR/J mice was substituted with the Fv-1b allele, thereby limiting viral replication and spread of the endogenous N-tropic murine leukemia virus. As a result of this restriction in virus spread, AKR-Fv-1b mice develop a low spontaneous incidence (7%) of T-cell lymphomas and about 28% of Ly-1+ B-cell lymphomas at old age. In spleens of 15–18-month-old thymectomized AKR/J mice and intact AKR-Fv-1b mice, 30–60% of the B-cells were of the Ly-1+ B type. Analysis of the IgH locus in these normal old spleens and Ly-1+ B lymphomas indicated mono- or oligoclonality. One particular IgH rearrangement was identified in many individual old spleens and tumors. A second specific IgH rearrangement was found in some tumors. Possible mechanisms involved in the expansion of Ly-1+ clones and their progression into tumors are discussed.


This work was supported by the Leo and Julia Forschheimer Center for Molecular Genetics at the Weizmann Institute and by the Israel Science Foundation (Grant 147/91). N. H. G. holds the Olin Sang Professorial Chair in Leukemia Research, and E. C. holds the Harry Kay Professorial Chair in Cancer Research.

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