Immune properties of M2 with prolonged culture and differentiation. (A) Expression of MHC‐Ib (Top) and MHC‐II (bottom) of M2P5. (B) Expression of MHC‐Ib (Top) and MHC‐II (bottom) of M2P36. (C) Expression of MHC‐Ib (Top) and MHC‐II (bottom) of M2P5 differentiated osteogenic cells (DOC). Open peaks were controls, representing unstained cells. (D) Two combinations of mixed lymphocyte culture. One was the co‐culture of naïve Balb/c (Bc) mononuclear cells (MNC) with M2P5 or M2P14 or M2P5DOC or M2P10DOC. For this group, x‐axis labels are ‘No C57 MNC’. Dark bars were controls, representing the count per minute of Bc MNC alone without the addition of any other cells in each test. The other combination was the co‐culture of Bc MNC and inactivated C57BL/6 (C57) MNC in the presence of M2P5 or M2P14 or M2P5DOC or M2P10DOC. For this group, x‐axis labels are ‘C57 MNC co‐culture’. The dark bars are controls, representing the count per minute of Bc MNC under the stimulation of inactivated C57 MNC in the same testing. Bars represent mean ± S.E. of triplicates of two independent experiments (*, P < 0.05; **, P < 0.01).