Serum antibody to SLA^dd cells after single administration of cells. Control animals injected with 1 × 10⁸ PBMCs (A) demonstrated production of IgG antibody to SLA^dd PBMCs within 2 weeks of injection. Animals receiving one injection of 10⁸ unactivated UTCs either intravenously or subcutaneously (B) did not have detectable antibody. IgG antibody production was also seen in animals injected with 10⁸ activated UTCs (aUTCs) expressing MHCII (C) and in animals receiving 10⁸ UTCs injected around an inflammatory lesion (CFA/UTC) (D), as well as after in animals receiving repeated doses (10⁸ cells/dose) of UTCs (E).