Antibody levels. Blood anti-EGFP antibody levels in Ly5.1 (control) and EGFP-chimeric (experimental) mice grafted with EGFP-expressing skin before (□) and after (▪) challenge with EGFP.Tg splenocytes (SPL). Values represent mean ± 1 SEM for groups of 5 mice at 62 weeks after BMT.