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Granulocytes are the major players in innate immunity and are prognostic markers in diseases. An in-depth phenotypic characterization of granulocyte subtypes and correlation with biometry or lifestyle is so far lacking. The reason is, that either preparation of mononuclear cells was analyzed or that cells in the neutrophil window were neglected in the analysis. Here we show for the first time lymphocyte- (LL) and monocyte-like (ML) cells within the granulocyte scatter gate as new, previously unknown cell subpopulation.
Immunophenotyping of 905 healthy German adults from the LIFE study [1] was performed by 10-color flow cytometry [2]. Age of men (n=420): 56.5±14.0 years, women (n=485): 56.7±13.6 y (range of 18-81 y). Data analyzed by FlowJo v10.0.6. Values compared by Mann-Whitney-U test: men vs women, young (18-49 y) vs. elderly (50-81 y.) men, and young (19-49 y.) vs. elderly (50-81 y.) women; significance: p<0.05.
Within the granulocyte gate four phenotypically distinct cell types were detected (all CD45+, SSCmid-high):
LL1 CD3+,CD4+,CD8++,CD16/56+,CD38+,HLA-DR+
LL2 CD3+,CD4low,CD8+,CD38low
LL3 CD3+,CD4+,CD8-
ML1 CD3-,CD4low,CD14+,CD38+
LL2 counts were increased in men (p=0.042), as well as ML1 counts (p <0.001). Most of the cell counts were not dependent on age, except LL2 in women. In conclusion, new lymphocyte like cell types with the neutrophil scatter characteristics are reported. Counts correlate with age and gender. We plan to sort these new subtypes for further functional characterization and aim to establish them as cellular biomarkers for the early detection of various diseases.
[1] BMC Public Health. 2015;15:691; [2] Cytometry A. 2014;85(9):781
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