Macrophage protein levels of Dnase1l3 and secreted FD-nuclease activity from BXSB, NZBW, MRL and BL6. This figure represents graphically the mean pixel volumes from Table 1. (a) FD-nuclease activity (RDA) secreted by macrophages was lower in NZBW and MRL-lpr mice relative to BL/6 (n = 15, both P < 0·01). (b) Immunoblot levels of Dnase1l3 protein in cell lysates from both populations were significantly elevated (n = 11 blots, P < 0·01). Thus, relative to their induced levels of Dnase1l3, macrophages from 89I SLE mice were deficient in secreted DNASE activity.