Changes in SCM-responses of lymphocytes in mice after implantation with ehrlich ascites cells

BDF-1 mice implanted for various times and with different numbers of Ehrlich ascites cells were used as a model system to find out how early in the development of neoplasia the SCM-responding subpopulation of lymphocytes can detect cancer (SCM-test), as assessed by changes in intracellular fluorescein polarization in response to stimulation with phytohaemagglutinin and ascites cell extract (ACE). One hour after implantation of 7.5 × 10⁵ ascites cells SCM-responses to ACE were induced and PHA responses abrogated. At the threshold number of 3.5 × 10⁵ ascites cells per animal SCM-responses to both ACE and PHA were observed. Ascites cells killed by radiation did not induce changes in SCM-responses. Extrapolation of these data on the basis of body weight ratio indicates that a human tumour load of less than 10⁹ cancer cells might be detectable in the SCM-test.