Morphology surface of a mouse plasmacytoma (LPC-1) showing cyclic resistance to immune lysis.

The murine BALB/c myeloma LPC-1 demonstrates a periodic resistance to lysis by immune mechanisms; this correlates with the production and accumulation of a trypsin-sensitive, single chain glycoprotein of 160 kilodaltons gp160 on the tumor cell surface. Tumor cells obtained 4 days after transplantation are lysed by cytotoxic T lymphocytes whereas ten-day cells are resistant to lysis. The progressive resistance to lysis was correlated with an increasing amount of gp160 on the surface of LPC-1 cells. Cell surface morphology, as determined by scanning electron microscopy, showed that early cells consisted of equal proportions of cells having microvilli or ruffles. The late cell population consisted mainly of cells with microvilli. These microvilli were twice as abundant on late LPC-1 cells as on early cells. Transmission electron microscopy images of late LPC-1 cells suggested an active protein synthesis which correlated with a more intense deposition of ruthenium red and an increasing amount of gp160 on the cell surface.