Research Paper Volume 11, Issue 24 pp 11955—11974

Platelet-derived β2m regulates age related monocyte/macrophage functions

Figure 1. A lack of platelet-derived β2M changes age associated monocyte phenotypes. (A) Platelets are a major source of age associated increases in plasma β2M. Plasma was isolated from 2-4 and 14-16 mos old WT and Plt-β2M-/- mice and β2M was quantified by ELISA. Plasma β2M had a greater increase with age in WT compared to Plt-β2M-/- mice (N=11, mean ± SEM, *P<0.05, **P<0.01, one-way ANOVA with Bonferroni correction). (B) Platelet MHC I increased with age. Platelets were isolated from 4 and 14 mos old WT and Plt-β2M-/- mice. Surface MHC I was quantified by flow cytometry. MHC I increased with age in WT, but not Plt-β2M-/- mice (N=3-4, mean ± SEM, **P<0.01, one-way ANOVA with Bonferroni correction). (C) Plasma TGFβ does not significantly change with age in either WT or Plt-β2M-/- mice. Plasma TGFβ was quantified by ELISA (N=17-24, mean ± SEM, one-way ANOVA with Bonferroni correction). (D) Aged Plt-β2M-/- mice had fewer circulating Ly6CHi monocytes compared to WT mice. Peripheral blood was isolated from 4 mos and 14 mos old WT and Plt-β2M-/- mice and monocyte Ly6C expression determined by flow cytometry. Ly6CHi monocytes were increased in older WT, but not Plt-β2M-/- mice (N=8-31, mean ± SEM, **P<0.01, one-way ANOVA with Bonferroni correction). (E) 14 mos old WT mice have increased plasma KC while Plt-β2M-/- have increased plasma IL-10 (N=16-22, mean ± SEM, one-way ANOVA with Bonferroni correction). (F) 14 mos old WT and Plt-β2M-/- mice had similar circulating neutrophils. Peripheral blood was isolated from 4 mos and 14 mos old WT and Plt-β2M-/- mice and CXCR2Hi and CXCR4Hi neutrophils were quantified by flow cytometry (N=5-9, mean ± SEM, one-way ANOVA with Bonferroni correction). (G) 14 mos old WT and Plt-β2M-/- mice have similar numbers of circulating T cells. Peripheral blood was isolated from 4 mos and 14 mos old WT and Plt-β2M-/- mice and CD4 and CD8 T cells quantified by flow cytometry (N=6-9, mean ± SEM, one-way ANOVA with Bonferroni correction).