Functional analyses of B cells in (NZW x BXSB) F1 mice.

Functions of B cells from (NZW x BXSB)F1 (W/BF1) mice are investigated. The W/BF1 mouse, which is an animal model for systemic lupus erythematosus (SLE) and immune thrombocytopenic purpura (ITP), produces anti-DNA and anti-platelet antibodies; W/BF1 mice show hypergammaglobulinemia (particularly increases in IgG2a and IgG2b). The ratio of small resting B cells to large activated B cells in W/BF1 mice is low compared to normal mice, suggesting that B cells in W/BF1 mice are already activated in vivo. Furthermore, small resting B cells separated by a Percoll density gradient technique show hyper-responsiveness to lipopolysaccharide (LPS) or anti-mu plus IL-4. This suggests that B cells in W/BF1 mice are genetically programmed to be easily activated, resulting in the overproduction of autoantibodies. A significant number of CD5+ B cells are found in the lymph nodes of old W/BF1 mice. These findings indicate that all cells in the B cell lineage of W/BF1 mice are already activated in vivo.