Characterisation of a new murine B cell lymphoma.

The characterisation of a new murine B cell lymphoma, A31, is described. Histopathological examination of passaged tumour indicates that initial infiltration occurs in the spleen, lymph nodes, Peyer's patches and liver, while in the terminal phase the bone marrow, gonads and occasionally the central nervous system become involved. The terminal spread is coincidental with the leukaemic phase in the tumour. The tumour cells show typical B cell characteristics in vitro. These include surface immunoglobulin (Ig) of mu, kappa isotype, surface Ia, Thy-1 negativity and an increased uptake of tritiated thymidine following incubation with lipopolysaccharide. A31 cells secrete low levels of IgM into the tissue culture fluid. Short-term culture produced only 100 ng IgM per 10(7) cells over 8 h and no tumour-associated monoclonal band could be detected in the serum of tumour-bearing mice. Chromosomal karyotypes of A31 cells gave model numbers 2n=40 normal, and 2n=41, with partial trisomy of chromosome 2, and trisomy of 17. There was loss of a chromosome 6 and the Y chromosome, together with the translocation of part of an 11 to one of the two unidentified marker chromosomes. The responses of lymphoma-bearing mice to therapeutic levels of cyclophosphamide and vincristine sulphate and also to whole body X-radiation are illustrated. This tumour may help in unravelling the complex biology of B cell lymphoma and because of its low level of Ig secretion, be of particular value in experimental immunotherapy.