Age-associated B-cells predict coronary events in humans and aggravate murine atherosclerosis

Aging is a major risk factor for cardiovascular disease (CVD) and is also linked to a functional decline of the immune system. B-cells contribute to atherosclerosis progression by antibody secretion, antigen presentation and T-cell regulation. During aging, CD11c + CD21low B-cells accumulate, but it is unclear whether these age-associated B-cells (ABCs) are linked with incident cardiovascular events in humans and if they contribute to the progression of atherosclerosis.

To investigate associations with first-time coronary events, circulating B-cells were phenotyped with flow cytometry in a case-control study (N = 604) nested in the Malmö Diet and Cancer Study cohort with a median of 14 years follow-up. Splenic B-cells in young (5 months) and aged (21 months) female Ldlr-/- mice were characterized with single-cell RNA-sequencing coupled with B-cell receptor (BCR)-sequencing. Atherogenicity of ABCs was determined by adoptive transfer to Ldlr-/- and Ldlr-/-Rag1-/- mice.Compared with other B-cell populations, ABCs showed a significant positive correlation with age (Spearman's rho 0.24; P < 0.0001; across 46-68 years of age) and accumulated in aged atherosclerotic mice. Coronary event cases had higher counts of ABCs than controls and regression analysis revealed an association with incident coronary events, that was independent of cardiovascular risk factors [odds ratio: 1.92 (95% CI 1.13-3.27), P = 0.016, comparing the 4th vs 1st quartile]. Adoptive transfer of ABCs to recipient mice promoted atherosclerotic lesion development. In Ldlr-/- Rag1-/- mice, ABCs also increased necrotic cores (P < 0.05). B-cells recovered from recipient mice after transfer expressed CD138 and secreted antibodies. In line with these findings, we demonstrated that ABCs expressed plasma cell differentiation genes and showed the greatest clonal expansion within the B-cell compartment, with extensive clonal overlap with plasma cells.

We show that ABCs predict first-time coronary events in humans and contribute to the immunopathology of atherosclerosis in mice, indicating that clonal expansion and accumulation of ABCs contribute to the strong association between age and CVD. ABCs may serve as potential prognostic and therapeutic targets for CVD.