Arthrofibrosis - Result of a T cell mediated immune response?

Aim: Detection of a T cell mediated immune response as a cause of arthrofibrosis. Methods: Tissue samples were taken from 7 patients (mean age: 31.8 years; range 18-50) undergoing open arthrolysis of the knee joint because of symptomatic arthrofibrosis following ligament injuries. The average time interval between trauma and arthrolysis was 16.4 months (range 4-48 m). Before arthrolysis, the mean range of motion was 77.8 degrees C (70 -110 degrees). Any other inflammatory disease was excluded by history. Tissue samples were fixed in formalin and embedded in paraffin. Sections were stained with HE. Monoclonal antibodies were used for immunohistological localization of MHC class II expressing cells as well as CD68, CD83, CD3, CD4, CD25 and CD20 positive cells. The ABC reaction and DAB or AEC were used for immunostaining and hemalum for counterstaining. Synovial tissue samples from 5 knees without any pathology served as controls. Results: Arthrofibrotic tissue revealed synovial hyperplasia, fibrotic enlargement and infiltration of inflammatory cells. Expression of MHC class II indicating antigen-presenting cells is increased in synovial macrophages (CD68+) and dendritic cells (CD83+). Positive immunostaining for CD4 (helper T cells) was also increased and mainly present around MHC class II expressing cells. There were also CD3+, CD25+ and CD20+ cells. Conclusion: A T cell mediated immune response may play a crucial role in the mechanism of arthrofibrosis. MHC class II expressing cells can present antigens that are recognized by helper T cells. This promotes an immune response followed by stimulation of other cells and formation of extracellular matrix.