3.2 Lower Tregs in IP sites of AA
HSCs have been mainly detected in close proximity to vasculature and the
endosteum, which is the osteoblast niche9. Tregs
accumulate in bone marrow and provide protection for HSCs via IP
mechanisms. Therefore, FoxP3/CD4 should be able to indicate the immune
tolerance status provided by IP to HSCs, especially in the area near
endosteum, which has been identified as an IP site, overlapping with the
osteoblast niche. We observed FoxP3+,
CD4+ and CD3+ cells near the
endosteum(Figure 1). FoxP3+/CD4+were significantly lower in AA than in normal controls (18.09%±5.38%vs . 21.72%±4.21%, P <0.05) and MDS
(18.09%±5.38% vs . 22.63%±5.98%, P <0.05)
(Figure 2A). Taking the low number of Tregs in bone marrow into account,
we tried to use the absolute count of FoxP3+ cells to
represent bone marrow immune tolerance status. The average number of
Tregs in AA was also significantly lower than that in normal control
(4.07±1.41 vs . 5.25±1.86 cells/HP, P <0.05) and
MDS (4.07±1.41 vs . 5.30±1.49 cells/HP, P <0.05)
(Figure 2B). No matter FoxP3+/CD4+or FoxP3+ absolute count, there was no statistically
significant difference between MDS patients and normal controls
(P >0.05).