Fig. 8. CHS in chimeric mice depends on environmental SPARC. (A) SPARC^+/+>SPARC^–/– chimeric mice expressing SPARC only in their BM compartment and reciprocal SPARC^–/–>SPARC^+/+ chimeras were obtained by using, respectively, (CB6)F1 mice as donor or recipient in BM transplantation experiments. To ensure that LCs were of donor origin, chimeras were UV-irradiated 8 weeks later to allow LC renewal from BM precursors. Three weeks after radiation, chimeric and control mice (UV-irradiated or not) were tested for CHS. (B) Immunostaining of MHC-II haplotype in the epidermal sheet of SPARC^+/+>SPARC^–/– chimera before and after UV-irradiation at the indicated time points. (C) The degree of CHS was dependent on the host rather than donor SPARC genotype, with greater CHS in SPARC^+/+>SPARC^–/– chimeras, which did not differ from SPARC^–/– control mice. No differences in ear swelling degree were detected in UV-irradiated and non-irradiated mice after replenishment of LCs from BM precursors, further confirming the role of environmental SPARC.