Increased PKC signaling in lupus La reactive B cells promotes development of the transitional T3 population and memory B cells in autoimmune BXD2 mice (BA3P.108)

We recently identified that lupus prone BXD2 mice exhibited defective clearance of apoptotic debris. I n vivo administration of excessive autologous apoptotic cells lead to elevation of IgG anti-La 13-27 responses in BXD2 mice but not normal B6 mice, suggesting chronic self-antigen stimulation plus B-cell tolerance defects may be related to the IgG anti-La 13-27 responses. To interrogate if there was abnormal maturation of anti-La 13-27 B cells in naive BXD2 mice, a recently developed La 13-27 tetramer was used with CD80 and PD-L2 co-staining to reveal that there was a significantly higher frequency of memory CD80 + PD-L2 + La 13-27 + B cells in BXD2 (17%), compared to that in B6 (3%) mouse spleens. Tetramer analysis of CD93 + transitional B cells showed that there was an abnormal skewing of the La 13-27 + T3 population, but not T1 or T2 B cells, in BXD2 (40%) compared to that in B6 (18%) mouse spleens. Survival of anti-La 13-27 producing B cells in BXD2 but not B6 mice was associated with increased protein kinase C (PKC) activation, as stimulation of B cells with PMA+ionomycin which promotes survival of BCR stimulated transitional B cells resulted in an increase in IgG. As T3 B cells are considered anergic B cells maintaining self-tolerance through rapid turnover in vivo , the abnormal expansion of these B cells coupled with increased BCR signaling response in BXD2 mice may present a risk for B-cell tolerance loss to La 13-27 , leading to maturation into IgG secreting cells.