B cell and T cell populations are altered in the brain‐draining lymph nodes of the senescence accelerated mouse prone 8 (SAMP8)

Abstract

AbstractBackgroundRecent studies have (re)‐discovered lymphatic vessels in the meninges and other sites that flow from the brain to deep cervical lymph nodes (dcLNs). Like elsewhere in the body, these lymphatic vessels play a critical role in the clearance of fluid and macromolecules from the brain including Aβ (a toxic protein that accumulates in the brain in Alzheimer’s disease) and in trafficking immune cells to the dcLNs, where immune activation occurs. The current study examined whether the immune cell populations are altered in the dcLNs of SAMP8 mice (a mouse model of accelerated aging with spontaneous overproduction of amyloid precursor protein in the brain) compared to the healthy control mice (SAMR1).MethodIn this study, dcLNs were collected from 12‐month‐old SAMP8 and SAMR1 mice (n = 6). Cells were isolated from the dcLNs, and the B cell and T cell populations (CD19 for B cells, PNA for germinal centre B cells, CD93 for early B cells, CD138 for antibody secreting B cells; CD3 for T cells, CD8a for cytotoxic T cells, CD4 for helper T cell) were studied using flow cytometry.ResultA significant 1.4‐fold increase in CD3+ T cells (p = 0.04) and a trend toward a decrease in CD19+ B cells (p = 0.06) was observed in the SAMP8 dcLNs compared with SAMR1 dcLNs. For B cell sub‐populations, a 77.9 ± 26.9% decrease (p = 0.0078) in geminal center B cells was observed in SAMP8 dcLNs. The T/B cell ratio was significantly increased in SAMP8 dcLNs (2.74 ± 0.14) comparing to SAMR1 dcLNs (2.10 ± 0.16). Such alteration was not observed in mesenteric lymph nodes.ConclusionThe B cell and T cell populations were altered in the brain‐draining dcLNs of SAMP8 mice, suggesting that the dcLNs responded to pathological changes in the brain. The reduced B cells, especially the germinal centre B cells, indicate a possible impairment in the production of antibody‐secreting B cells in SAMP8 mice. We will confirm these observations in APP/PS1 and 5xFAD mice in future studies, and investigate whether such alteration in B cells contributes to Alzheimer’s disease pathology.