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- Title
Immunohistochemical characterisation of immune cells in fixed equine endometrial tissue: a diagnostic relevant method.
- Authors
Rudolph, Nicole; Schoon, Heinz-Adolf; Schöniger, Sandra
- Abstract
Endometrial diseases are the major cause of subfertility in mares. The detection of subclinical diseases requires the histopathological examination of an endometrial biopsy. To prevent autolysis endometrial biopsies have to be fixed prior to their submission to the diagnostic laboratory. The most frequent type of chronic subclinical inflammation is non-suppurative endometritis. An immune mediated pathogenesis is suspected. Type 1 and type 2 adaptive immune responses exist; these are mediated by CD4+ helper T cells, CD8+ cytotoxic T cells, CD20+ B cells, plasma cells as well as polarized macrophages. In equine research, CD172a has been proposed as panmacrophage marker, CD14 and CD206 as markers of M1 and M2 polarisation, respectively; immunostaining for these antigens was only performed on cryostat sections of unfixed equine tissue. The aim of the present study was a) to establish an immunohistochemical method for the detection of macrophages in fixed equine tissue samples and b) to characterize the immune cell populations in fixed endometria with and without chronic endometritis. In regard to the former objective, immunostaining for CD172a, CD14 and CD206 was performed on paraffin embedded equine tissue with resident macrophages (lymph node, liver, small intestines) fixed either with IHC Zinc Fixative or 10% neutral buffered formalin. In regard to the latter, immune cell populations in zinc fixed paraffin embedded (ZnFPE) endometrial biopsies of mares without endometritis (n=4) and those with a superficial non-suppurative endometritis (n=28) were compared. This study established an immunohistochemical method for the detection of the examined macrophage markers within fixed tissue samples, i.e. ZnFPE (CD172a, CD14, CD206) and formalin fixed paraffin embedded (FFPE) tissue after antigen retrieval (CD172a, CD206). It indicated that CD172a likely represents a pan-macrophage marker also in the equine endometrium. Immunohistochemical phenotyping showed that non-suppurative endometritis is mainly a T cell mediated disease with participation of plasma cells. In addition to CD4+ and CD8+ T cells, results indicate the presence of CD4-/CD8- double negative T cells. B cells and/or macrophages were observed in 15 cases. Endometrial macrophages expressed mainly CD172a and only rarely CD206, whereas CD14 was not detected. Notably, examined endometria showed a high variability in the numbers of T cell populations as well as plasma cells. This suggests the existence of subforms of this disease that may even differ in pathogenesis and etiology. The established method of immunophenotyping can be included in the routine diagnostic work-up of equine endometrial biopsies and can be beneficial for the identification of new therapeutic approaches. Its standardized application will likely assist to uncover immunological features that may predispose mares to develop persistent endometritis. The successful future application of this method will likely be beneficial for the genital health of individual mares, it also may help to prevent financial losses of the horse breeding industry.
- Subjects
IMMUNOLOGIC diseases; ENDOMETRIAL diseases; FORMALDEHYDE; MACROPHAGES; HORSE breeding
- Publication
Pferdeheilkunde, 2017, Vol 33, Issue 6, p524
- ISSN
0177-7726
- Publication type
Article
- DOI
10.21836/PEM20170601