CD4 and periodontitis: Under the Treg polarization condition, the periodontitis BM-MSCs behaved dramatically different from the normal BM-MSCs, as the observations on higher percentage of CD4+CD25+FoxP3+ Treg population (Figure 2D), as well as the higher expression of FoxP3 mRNA and IL-10 production in culture medium (Figure 2E), in comparison to the group with the T cells co-cultured with normal BM-MSCs.