Induction of murine CD5 expression by v-H-ras

The murine CD5 surface antigen is a frequent marker on B-lineage cell lines produced from bone marrow infected with retroviruses expressing v-H-ras. Since CD5+ B cells cannot be detected in adult murine bone marrow, either the viral targets of transformation are a minor contaminating population of CD5+ B-lineage cells or the v-H-ras oncogene is inducing the expression of CD5 on B-lineage cells not previously expressing this marker. We have found that v-H-ras can induce the expression of CD5 on two CD5+ pre-B-cell lines established from murine bone marrow. This induction correlates with increased steady-state levels of CD5 mRNA. These results present the possibility that CD5 expression may be modulated by specific signalling as well as early lineage commitment.