With age, humans and mice experience higher antigen exposure and an increased proinflammatory environment. Furthermore, the number of FOB, MZB and B1b/a cells decrease as ABC accumulate with age. This can be replicated in chronically infected and autoimmune-prone young mice, which accumulate CD11c+Tbet+ ABC. T-cell responses also decrease leading to a higher dependence on PR signals. Unlike, T-cell dependent FOB, ABC can be T-independent, and their activation depends on higher Ag exposure and PR signals. Thus, they can mount a primary response to new pathogens, which may provide protection.