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The presence of NKG2A, NKG2C and NKG2D potential receptors for HSP70 in synovial tissue of patients with osteoarthritis

INTRODUCTION: The stress-inducible heat shock protein 70 (HSP70) is frequently upregulated in a disease state, therefore it increases in chondrocytes, synovial fluid and sera of patient with osteoarthritis (OA) comparing to healthy control. HSP70 relates to joint inflammation and severity of OA, as well as to the infiltration of synovial tissue with NK cells. AIM: To analyze the presence and distribution of NK cell receptors of C type lectin family, as potential receptors for HSP70 in synovial tissue. MATERIAL AND METHODS: Mature synovial tissue samples were obtained during the knee alloarthroplasty. NKG2A, NKG2C and NKG2D were identified in paraffin-embedded tissue sections by immunofluorescence. Two independent observers counted the cells labeled with particular antibody in five different synovial samples at field magnification x400 of the fluorescent microscope and expressed the results as average ± standard deviation of the number of positive cells. RESULTS: Mature synovial tissue contains 46 ± 13 NKG2A expressing cells, 38 + 18 NKG2C expressing cells and 28 ± 16 NKG2D expressing cells per field at magnification x400. All three receptors were found in synovial lymphocyte accumulations. Additionally, NKG2A and NKG2C were scattered in sublining synovial tissue, while NKG2D was present on the surface of synovial shoots. The distribution of the receptors resembles to the distribution of synovia NKp46+ NK cells. CONCLUSION: The presence of NKG2A, NKG2C and NKG2D expressing cells in synovial tissue suggests that they are potentially able to bind HSP 70 and directly support local pro-inflammatory response.

heat shock protein 70 ; C type lectin family receptors ; osteoarthritis ; synovial tissue

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