Carriers of the p.P522R variant in PLCγ2 have a slightly more responsive immune system

Abstract

Background The rs72824905 single-nucleotide polymorphism in the PLCG2 gene, encoding the p.P522R residue change in Phospholipase C gamma 2 (PLCγ2), associates with protection against several dementia subtypes and with increased likelihood of longevity. Cell lines and animal models indicated that p.P522R is a functional hypermorph. We aimed to confirm this in human circulating peripheral immune cells. Methods We compared effects of p.P522R on immune system function between carriers and non-carriers (aged 59-103y), using in-depth immunophenotyping, functional B-cell and myeloid cell assays, and in vivo SARS-CoV-2 vaccination. Results In line with expectations, p.P522R impacts immune cell function only slightly, but it does so across a wide array of immune cell types. Upon B-cell stimulation, we observed increased PLCγ2 phosphorylation and calcium release, suggesting increased B-cell sensitivity upon antigen recognition. Further, p.P522R-carriers had higher numbers of CD20++CD21-CD24+ naive B cells and IgG1+ memory B cells. In myeloid cells, normalized ROS production was higher upon PLCγ2-dependent stimulation. On classical monocytes, CD33 levels were elevated. Furthermore, carriers expressed lower levels of allergy-related FcεRI on several immune cell subsets. Nevertheless, carriers and non-carriers had similar serological responses to SARS-CoV-2 vaccination. Conclusion The immune system from p.P522R-carriers is slightly more responsive to stimulation than in non-carriers.

The hypermorphic PLCγ2 S707Y variant dysregulates microglial cell function – insight into PLCγ2 activation in brain health and disease, and opportunities for therapeutic modulation

“…Although both deficient and hyperactivated PLCγ2 impair microglial function in a similar way, our RNASeq data suggests minimal overlap in mechanism, supporting the clear need to dissect the impact of each specific variant on cellular functionality [32]. We hypothesise that the PLCγ2 P522R variant lies in the "protective" zone, whereby the mild hypermorphic activity is beneficial to immune function, and not detrimentally impacting the immune response as observed for the strong hypermorphic PLCγ2 S707Y variant and the PLCγ2-deficient hiPSC-derived microglia [32,52,53]. hiPSC-derived microglia expressing PLCγ2 P522R and knock-in PLCγ2 P522R mice both show increased phagocytic activity towards amyloid-beta 1-42 [18,19,51].…”

Performance of spectral flow cytometry and mass cytometry for the study of innate myeloid cell populations

“…Two antibody panels specifically designed for the study of IMC populations were used to stain PBMC, based on previous reports (EuroFlow patent "Means and methods for multiparameter cytometry-based leukocyte subsetting"; PCT/NL2020/050688, priority date 5 November 2019) (27,(32)(33)(34)(35)(36). Briefly, the selection of the markers employed in both MC and SFC combinations was performed based on unbiased identification of the most optimal set of markers to identify each population, in order to provide the best population discrimination and avoid any type of redundancy (27, 37-41).…”