Lymphocyte subsets in stifle joint synovial fluid of dogs with spontaneous rupture of the cranial cruciate ligament

Abstract

Synovial fluid samples from 64 stifles of 54 dogs with spontaneous rupture of the cranial cruciate ligament were investigated for total and differential leukocyte counts and lymphocyte subsets using the methods of flow cytometry and anti-canine monoclonal antibodies. Synovial fluid samples from 19 healthy (without lameness, pain, macroscopic and roentgenological changes) joints of 12 dogs were used as a control. Total and differential leukocyte counts from joints after cranial cruciate ligament rupture did not differ from healthy joints. Less than 5 × 106 leukocytes per millilitre were detected and neutrophils constituted less than 5% of all leukocytes. Percentages of lymphocytes expressing CD4 and CD8 were higher in synovial fluid from joints after cranial cruciate ligament rupture. On the other hand, percentages of lymphocytes expressing the CD45RA isoform were significantly lower in synovial fluid from joints after cranial cruciate ligament rupture. Results show some role of cell-mediated immunity in pathogenesis of spontaneous rupture of the cranial cruciate ligament.