Effect of leukopenia and leukocytosis on tumor growth and survival time.Part I. Leukopenia

The study was performed with 174 rabbits to determine the effect of leukophoresis and the resulting leukopenia on tumor transplant, growth, and survival time using the V2 carcinoma in the rabbit. Definite inhibition of tumor growth, together with increase in survival time, was found when leukophoresis was performed 7-28 days after transplant as evidenced by an increase in survival time of 314 days in the entire group receiving 2 leukophoreses following transplants and 347 days in subgroups of those receiving 3 leukophoreses following transplants (but on days 7-14-21 or 14-21-28) vs. 73 days for the controls. The tumor growth rate paralleled the survival time and following transplant and leukophoresis, the increase and decrease of leukocytes paralleled the rate of tumor growth and retardation, respectively. There is reason to believe that the granulocyte may be more implicated than lymphocyte in tumor inhibition and survival time although so far experimental evidence has been on the side of the latter. A chance observation that leukophoretic plasma injected into cancerous and noncancerous animals produced marked leukocytosis, indicating a leukocytosis-inducing factor, will serve to investigate any significant effects of leukocytosis on tumor growth and survival time and any possible interrelationship of leukopenia/leukocytosis to tumor inhibition and immunosuppression in Part II of this paper.