Aging disrupts the affinity threshold for naïve B cell germinal center participation 2306948

Abstract Introduction Vaccination is a crucial public health measure that provides protection from infectious pathogens, but protection is reduced in aged individuals due to waning immune responses. One correlate of protective immunity is the production of high affinity antibodies by germinal centers, which are known to be severely impaired in aged organisms due primarily to a reduction in T cell help. Less is known about how aging affects naïve B cells prior to an immune response. Here, we sought to address how naïve B cells in old (2 years of age) mice performed in an immune response compared to B cells in young mice (8 weeks of age). Methods We studied naïve B cells from old or young mice using adoptive transfer into young B cell knockout mice, followed by immunization with nitrophenyl-chicken gamma globulin (NP-CGG) in alum. B cell responses were characterized using flow cytometry, scRNA-seq, and scBCR-seq. Individual antibodies were cloned from responding B cells and their affinities were measured using biolayer interferometry. Results Upon immunization, mice that received B cells from old donors generated significantly more germinal center B cells than those that received young donor cells, but a smaller percentage of the old cells were specific for NP. scBCR-seq of responding old GC B cells revealed increased usage of less common heavy and light chain pairings. Recombinant antibodies produced by these cells had reduced affinity for NP than those produced by young GC B cells. Furthermore, scRNA-seq of GC B cells and naïve B cells suggested that old B cells have a signature of activation even prior to immunization, which was supported by increased phosphorylation of protein kinases in old naïve B cells. Conclusion We found that during aging, naïve B cells had increased basal stimulation that allowed the selection of lower affinity B cells into the germinal center reaction, resulting in the production of lower quality antibodies throughout the immune response. Funding Source National Institute on Aging Intramural Research Program Topic Categories Immune Response Regulation: Molecular Mechanisms (IRM)