Monoclonal anti-human T cell antibody and PAP-s conjugate--preparation and selective cytotoxic properties on leukemic cell.

Pokeweed antiviral protein (PAP-s) was prepared from seeds of Phytolacca americana. Monoclonal antibody against human pan-T lymphocyte Wu71 was linked to PAP-s by a disulfide bond. The results of SDS-PAGE, double immunodiffusion of active monoclonal antibody and PAP-s showed that the conjugate was highly cytotoxic to the human T-leukemic cell line CEM, but not to antigen-negative cell line SP2/O. At a concentration of 10(-9) mol/L, 76.4% of the target cells were killed, as compared with 10.1% at 10(-9) mol/L of free PAP-s. Treatment of the CEM cells with conjugate at 10(-9) mol/L reduced their rate of protein synthesis by 72.4%, as determined with 14C-leucine incorporation. The immunotoxin may be useful for the in-vitro eradication of leukemic cells in autologous bone marrow transplantation to leukemia patients.