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Immunohistochemical Analysis of Extensor Carpi Radialis Brevis Origin Tissue
Danielle M. Stoll, MS1; Owen J. Moy, MD2; Robert H. Ablove, MD1; Jonathan L. Tueting, MD3
1University Wisconsin Madison, Madison, WI; 2University at Buffalo, Buffalo, NY; 3University of Wisconsin School of Medicine and Public Health, Madison, WI

Hypothesis: The purpose of this study was to investigate the various cells present at the origin of extensor carpi radialis brevis (ECRB) tendon in late chronic stages of lateral epicondylitis. We specifically investigated the presence of t-cells, indicating a late adaptive immune response.
Methods: Chronic ECRB tendon from the origin of eighteen patients (10 male and 8 female) were extracted via the standard Nirschl procedure and flash frozen. Specimens were sectioned and mounted on glass slides (5um thickness). Mouse and rabbit monoclonal antibodies were used to detect the cells of interest. Primary antibodies consisted of CD31, CD3, CD 163, CD 68 or PCNA (Abcam; Cambridge, MA). Light microscopy was used for spatial localization and cell counting of immunohistochemistry stains. Additional histological stains (hematoxylin and eosin) were used to qualitatively measure the density of cells in the lesion and the degree of collagen disorganization.
Results: Immunohistochemical analysis revealed hypervascularity and hyperproliferating cells in the lesions (consistent with previous findings).1,2,3,4,5 In all specimens endothelial cells forming lumen to small vasculature were identified along with proliferating cells. In most specimens small quantities of CD68 and CD163 (macrophages I and II) were observed. The hematoxylin and eosin revealed a fair number of cells present in the specimens. CD-3 like immunoreactivity was noted suggesting presence of t-cells in the chronic tissue (figure 1). This presence of t-cells suggests that the adaptive immune system may partake in the late stages of lateral epicondylitis instead of the innate immune system. Disorganized collagen fibers were observed in all samples and were noted in areas of greater angiogenesis and cell proliferation (figure 2).


  • Endothelial cells forming the lumen to newly created small vasculature and proliferating cells were present in chronic ECRB tendon indicating hypervascularity and hyperproliferating cells.
  • Small quantities of macrophages I and II were present and findings consist with existing studies.6
  • Collagen appeared to be disorganized and unstructured in all collected tissue.
  • The role of the adaptive immune system has not been extensively explored in ECRB tendon. We investigated the presence of t-cell immunity and found it prevalent in all 18 samples. In the future we wish to determine the t-cell phenotype, to help accurately infer their role in the disease process. T-helper 1, and t-helper 17 cells would be the primary analyzed phenotypes. Th17 is seen in other chronic degenerative inflammatory diseases.7

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