Significance of arming, potentiating and blocking factors as correlates the tumour-host interaction in the hamster SV40 system.

The study of blocking factors requires in vitro assay of cell mediated immunity that parallels the in vivo response. By microcytotoxicity testing, progressor and immune peripheral blood lymphocytes caused significant target cell reduction. The cytotoxicity was specific as no cytotoxic effect was detected against unrelated normal as well as a malignant target cell lines. No anti-tumour effect was noted when progressor peripheral blood lymphocytes were evaluated in the Winn assay. In marked contrast, immune peripheral blood lymphocytes were capable of preventing tumour growth in the Winn assay. Furthermore, hamsters repeatedly immunized with irradiated SV40 tumour cells could resist a live cell challenge. Thus immune peripheral blood lymphocytes were chosen as the effector population to evaluate the abrogation ability of serum in the microcytotoxicity assay

Laminin production by murine melanoma cells: possible involvement in cell motility

Three lines of B16 melanoma cells (B16-F1, B16-F10 and B16-BL6) were examined for motility in the micropore filter assay and for synthesis in culture of the basal lamina glycoprotein laminin. All three lines synthesized laminin as judged by the incorporation of [ 35 S]methionine into immunoreactive laminin and secreted (or shed) laminin into the culture medium as indicated by biosynthetic labeling studies and enzyme-linked immunosorbent assays. Immunoreactive laminin was also seen on the surface of the cells as indicated by immunofluorescence staining and by complement-mediated killing. Analysis of [ 35 S]methionine-labeled laminin immunoprecipitates by sodium dodecylsulfatepolyacrylamide gel electrophoresis (SDS-PAGE) both with and without reduction of intersubunit disulfide bonds revealed that all three cell lines produced a similar array of laminin forms, and that the M r =950kD laminin molecule (but not the uncombined subunits) was secreted into the culture medium. Laminin biosynthesis appeared to be limited by the availability of the M r =400kD A subunit as shown by the intracellular accumulation of excess B subunit in the form of uncombined B subunit ( M r =200kD) and as a disulfide-linked B dimer ( M r =400 kD). The motility of all three cell lines was stimulated four- to five-fold by the addition of either exogenous laminin from the EHS sarcoma or culture medium from the B16 cells containing the secreted laminin. The stimulated motility was inhibited by antilaminin serum. These observations suggest that the laminin synthesized by the B16 melanoma cells themselves may facilitate their motility.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42594/1/10585_2004_Article_BF00133591.pd