Some Structural and Antigenic Properties of Intracisternal A Particles Occurring in Mouse Tumors

Abstract

Intracisternal A-particles were isolated from three different myeloma lines in BALB/c mice and from cultured neuroblastoma cells of A/J origin. All preparations contained a major structural protein with an apparent molecular weight near 70,000 as estimated by electrophoretic mobility in sodium dodecyl sulfate-containing polyacrylamide gels. Solubilization of this component by sodium dodecyl sulfate was dependent on prior or concomitant treatment with sulfhydryl compounds. The size distribution of A-particle proteins was markedly different from that observed for extracellular murine leukemia and mammary tumor viruses. Rabbit antiserum was developed that reacted with the major A-particle protein in both complement fixation and immunodiffusion assays. The antigen was detected in isolated neuroblastoma A-particles, in cytoplasmic membrane fractions prepared from various mouse tumors known to contain intracisternal particles, but not in preparations from normal mouse cells, in samples of leukemia and mammary tumor virus, or in JLS-V9 cells infected with Rauscher leukemia virus. Conversely, isolated A-particles did not react in complement fixation or immunodiffusion assays with antisera against leukemia virus antigens.