The effects of heme on the immune response. (A-B) Mice were injected intraperitoneally with heme (H) or vehicle (V; 3 mice/group) every other day (3 times; arrow). The total liver homogenates were obtained from these mice and tested for protein expression by a Western blotting analysis using antibodies to HO-1. (C-D) Mice were immunized with DNP-Ficoll with or without heme (Day 0), followed by intraperitoneal injection of heme (H; n = 6) or vehicle (V; n = 6) every other day (Days 2, 4: 2 times; arrow). Sera were collected on days 0 (dashed line) and 8 (solid line) and were assayed for DNP-specific antibodies (open circles, vehicle; open triangles, heme). The data are presented as the means ± SD (E-F) Mice were immunized with DNP-Ficoll (Day 0) and treated with heme as described previously. The amounts of DNP-specific antibodies (open circles, vehicle; open triangles, heme) are shown as described previously. (G) The proliferation of primary B cells stimulated with LPS in the presence or absence of heme for 2 days. Each symbol shows data from the same mouse.