FIG. 6.

Characteristics of the humoral response. The isotype and titer of the antibody response to ACI ASCs at 4 and 8 weeks is shown in (A) for No Trt and Allo+Scaf–treated rats. Rat sera were diluted as indicated, allowed to bind to ASCs and labeled with FITC-conjugated goat anti-IgM or IgG secondary antibodies before evaluation by flow cytometry. Significant differences from No Trt controls are denoted by an asterisk (p < 0.05). Sera from the same groups of rats were evaluated for cytotoxicity against ASC target cells (B). After allowing sera to bind ASCs, guinea pig complement was added, and cell viability was determined by propidium iodide staining and flow cytometry. As controls, ASCs were incubated with complement only (“None”) or with anti-CD90 mAb (positive control). The specificity of rat sera for FBS is shown in (C). Rat sera from all four groups in the spinal fusion study were serially diluted and evaluated for binding to FBS by ELISA. In all panels, the number of rat sera tested per group is shown in parentheses, and group means are shown ± standard error.