T- and B-cell determination in various lymphoid tissues of mice during N-nitrosobutylurea (NBU) leukemogenesis

T- and B-cell distribution in thymus, spleen, and lymph nodes has been investigated during chemical lymphomagenesis. N-nitrosobutylurea (0.04 g/100 ml) in drinking water was administered to 35-day-old male C57BL mice for a period of 60 days. As of week 11, 21 of 22 Nbu mice developed thymic lymphomas of lymphoblastic cell type which showed a general leukemic spread to spleen, lymph nodes, and several extralymphatic organs at week 16. Immunocytologic studies revealed the T-cell origin of these thymic type lymphomas. Alteration of the T-cell system during latency period was represented by reduced thymic weight, cell numbers, as well as absolute and relative T-cell reduction. Absolute T-cell reduction was also observed in the spleen, although the reduction of splenic lymphoid cells was mainly caused by a decrease of B cells. In lymph node subnormal variations of theta-positive cells took place, whereas B-cell distribution was not altered. An impaired T- and B-cell function was suspected from preleukemic changes of lymphoid subpopulations. The results are compared with other murine lymphomas and discussed with regard to a functional hypothesis of lymphomagenesis.