CD80 and Autoimmunity: Whilst there was a large increase in the frequencies of CD19+CD138+ (putatively plasmablasts) and CD19+CD80+ [activated and memory B cells (33)] in 4X infected mice compared with 1X infected mice, we also observed an increase in the frequencies of atypical CD19+ cells expressing CD11c [B cells that exert APC activity and may contribute to autoimmunity (13, 34–36)], PDCA-1 [suppressor B cells but which also produce Abs (37)] and PDL-1 [putatively regulatory B cells (38)] in 4X infected mice compared with 1X infected mice (Figure 4C).