Partial purification and characterization of an autocrine T suppressor factor from murine leukemia

The leukemia-associated autoinhibitor (LAI-615) derived from murine leukemia L7811 has been investigated intensively in our laboratory. In the following experiments, the partial purification of LAI-615 has been carried out in addition to the observation of phenotype variations of L7811 leukemic cells. The factor was purified over 1306-fold by sequential fractionation with Sephadex G-150 gel filtration, DEAE-cellulose ion exchange chromatography, and Mono Q-fast protein liquid chromatography. The molecular weight of LAI-615 was 68,000 as estimated by gel filtration. LAI-615 was a protein but not glycosylated, and it was suggested LAI-615 be secreted in an autocrine manner. Immunocytochemical staining showed that the expression of Lyt2 phenotype of L7811 leukemic cells was often coincident with the secretion of LAI-615. Moreover, the physicochemical characteristics of LAI-615 was similar to that of T suppressor factor. Thus it is concluded that LAI-615 may be one of TsF-like factors.