In vivo and in vitro effects of thymosin treatment in spontaneous and first transplant AKR leukemias

Thymosin is reported to restore a variety of T lymphocyte dependent immune responses. In the current studies, young AKR mice were implanted with subpopulations of leukemic lymphocytes (thymus, spleen, lymph nodes), and subsequently treated with 6 injections of thymosin over a 12 day period (Fraction V) or a control extract. Lymphocytes (thymus, spleen, lymph nodes) from treated and control mice were then examined for response to Concanavalin A (Con A) and phytohemagglutinin (PHA), and effect on survival was determined. Response to both Con A and PHA was increased in cultures of thymocytes derived from thymosin treated mice implanted with leukemic thymus cells, but decreased in lymph node cells from this group. Survival was not markedly altered in any of these groups. The homing patterns of subpopulations of lymphocytes from thymosin treated aged AKR mice without overt disease was also determined. A significant increase in the localization of lymphocytes from thymosin treated mice was noted in the thymuses of recipient animals. It is apparent that subpopulations of lymphocytes from AKR mice differentiate under the influence of thymosin. These data suggest that thymosin may play a significant role in spontaneous leukemogenesis in AKR mice.