IgM-PRODUCING TUMORS IN THE BALB/c MOUSE : A MODEL FOR B-CELL MATURATION

Five adjuvant induced BALB/c tumors producing IgM—McPc 1748, W 3469, TEPC 183, McPc 774, and Y 5781—were characterized morphologically by electron microscopy, analysis of the distribution of surface-bound and intracytoplasmic IgM using immunofluorescence, and by biochemical study of IgM synthesis, turnover, and secretion. The cells of different tumors appear to represent different stages in B-cell maturation when compared to normal, lipopolysaccharide-stimulated B cells. Thus, McPc 1748 tumor cells resemble 10–25-h stimulated normal B cells, 3469 cells resemble 20–35-h stimulated B cells, TEPC 183 cells resemble 45–65-h stimulated B cells, Y 5781 cells resemble 80–110-h stimulated B cells, and McPc 774 cells resemble 100–130-h stimulated B cells.