Abrogation of tumor induced Ly49 expression on mouse spleen cells by mitomycin C

Mouse spleen cells were activated with IL2 for 4 days in the presence or absence of paraformaldehyde fixed YAC (PFY) tumor cells (spleen cell: PFY ratio 100:1). Fresh spleen cells had poor expression of Ly49A but the expression was significantly upregulated by IL2 activation. Addition of PFYs resulted in a further boosting of Ly49A expression. Besides Ly49A, the Ly49C receptors were also upregulated by PFYs. Upregulated Ly49 expression was not restricted to NK cells (NK1.1 positive cells) but was also seen on T cells (TCRbeta positive cells). Time kinetics studies indicated that maximum upregulation of Ly49 in response to PFY cells occurred on day 3 and 4 and the expression declined thereafter. Ly49 expression in response to PFYs was completely blocked if spleen cells were pre-treated with Mitomycin C, an inhibitor of DNA synthesis. These results show that the addition of a small number of paraformaldehyde fixed YAC cells to spleen cell cultures undergoing IL2 activation, resulted in a significant upregulation of Ly49 receptors and this process was dependent upon cell proliferative activity.