Serial syngeneic transplantation of large granular lymphocyte leukemia in F344 rats

A spontaneous large granular lymphocyte (LGL) leukemia was serially transplanted in 92 male F344 rats kept under standard laboratory conditions. Serial transplantation into groups of four rats each resulted in a rapid reduction in the latent period of the disease. After 23 serial transplantations, F344 rats in groups that were injected intraperitoneally with 10(7) cells died between 12 and 16 days after transplantation. At necropsy, "transplanted" rats had enlarged mesenteric lymph nodes, thymus, and spleen. Neoplastic cells were detected in the spleen on day 3 and in peripheral blood on day 6. Extreme leukocytosis with leukemia was present on day 9. Severe hemolytic anemia coincided with a sharp increase in osmotic fragility on day 12. Splenic lymphoid depletion was observed histologically and confirmed by differential cell counts of isolated spleen cells. Analysis for surface markers of splenic lymphocytes by monoclonal antibodies and flow cytometry indicated that cells with T helper/inducer phenotypes were disproportionately decreased, while the number of T suppressor cells did not significantly change. The T helper/T suppressor lymphocyte ratio (normal = 2.09 +/- 0.35) was decreased on day 9 (0.76 +/- 0.10) and day 12 (0.25 +/- 0.04). Hemolytic anemia was not related to a decrease in the number of T suppressor cells. The passaged leukemia cell model should provide investigators with an easily maintained neoplasm of short latency with which to study pathogenesis of leukemia-related disorders.