Investigation of bone fracture repair in the presence of perturbed lymphocyte function

Recently the dynamic association between the immune system and the skeletal system has become appreciated. However, to date there has been no attempt at manipulating CD4+ and CD8+ T lymphocytes during fracture repair. This study was aimed at evaluating whether patients and animals with a perturbed lymphocyte function have an abnormal bone fracture repair.The in vivo study involved the creation of a standard closed tibia fracture in BALB-c mice depleted in CD4+ or CD8+ T lymphocytes compared to wild type controls. Bone fracture repair was investigated using radiographs, biomechanical testing, stereology and immunohistochemistry. The CD4+ depleted group had significantly greater callus size at days 7 and 14 compared to controls (p<0.001). Stereology confirmed a significantly greater proportion of bone than cartilage compared to the CD8+ depleted group. The CD8+ depleted group had a significantly greater callus size at days 7 and 21 post fracture compared to controls (p