Background: Arthroscopic anterior cruciate ligament (ACL) reconstruction with allograft may vary in instrumented laxity compared with autograft. T helper (Th) cells (CCR4+CCR6+Th) and regulatory T (Treg) cells are important in the early stage of immunologic reactions. It is unknown whether the ratio of CCR4+CCR6+Th to Treg is imbalanced and if it correlates with early postoperative laxity after ACL allograft reconstruction. We investigated the ratio and functional influence between these cells and the correlation with postoperative anterior knee laxity.
Methods: In 40 patients who experienced unilateral arthroscopy-assisted ACL reconstruction, the ACL graft was an allograft in 20 patients and autograft in 20 patients. Maximum manual anterior tibiofemoral laxity measurements were performed with arthrometry testing. The phenotypes of CCR4+CCR6+Th and Treg cells of peripheral blood and synovial fluid from the two patient groups were determined by flow cytometry. The functionality of isolated Treg cells and effector T cells was quantified in (3)H-thymidine proliferation assays.
Results: Both CCR4+CCR6+Th and Treg cells were significantly increased in the synovial fluid in the allograft group and were correlated with anterior knee laxity. The ratio of CCR4+CCR6+Th to Treg cells in the synovial fluid was positively correlated with laxity. Synovial CD4+CD25+ Treg cells displayed an increased suppressive capacity compared with blood CD4+CD25+ Treg cells. Activated responder T cells from the synovial fluid were less susceptible to CD4+CD25+ T cell-mediated suppression than were responder cells from blood.
Conclusions: The ratio of CCR4+CCR6+Th to Treg cells in the synovial fluid was correlated with anterior laxity after ACL allograft reconstruction.