MAPCs mediate suppression via a soluble factor. B6 > BALB/c MLR plus MAPCs at 1:10 ratio was arranged by placing T cells and stimulators in the lower well of a Transwell insert and MAPCs in the upper chamber, or by placing MAPCs in direct contact with stimulators and responders (A). (B) Supernatant taken from MAPC or control cocultures on day 3 was added in 1:1 ratio with fresh media to a B6 > BALB/c MLR. Results of MAPCs at 1:10 and 1:100 ratios in direct contact with responding T cells are shown for comparison. Proliferation was assessed using ³H-thymidine uptake. Enzyme-linked immunosorbent assay was performed on MLR supernatant harvested on the indicated day to determine the amount of proinflammatory (C) and anti-inflammatory (D) cytokines in culture with MAPCs at 1:10 and 1:100 ratios.