Lymphocyte Subsets in the Adrenal Glands of Dogs With Primary Hypoadrenocorticism

Abstract

Primary hypoadrenocorticism, or Addison's disease, is an autoimmune condition common in certain dog breeds that leads to the destruction of the adrenal cortex and a clinical syndrome involving anorexia, gastrointestinal upset, and electrolyte imbalances. Previous studies have demonstrated that this destruction is strongly associated with lymphocytic-plasmacytic inflammation and that the lymphocytes are primarily T cells. In this study, we used both immunohistochemistry and in situ hybridization to characterize the T-cell subtypes involved. We collected postmortem specimens of 5 dogs with primary hypoadrenocorticism and 2 control dogs and, using the aforementioned techniques, showed that the lymphocytes are primarily CD4+ rather than CD8+. These findings have important implications for improving our understanding of the pathogenesis and in searching for the underlying causative genetic polymorphisms.

Keywords: Addison’s disease; adrenal gland; dogs; endocrine diseases; hypoadrenocorticism; immunophenotype; lymphocyte subsets.

Figure 1

Primary hypoadrenocorticism, adrenal cortex, Dog 3. (a) Lymphocytes, plasma cells, and foamy macrophages densely infiltrate the adrenal cortex – Hematoxylin and eosin. (b) Same area of the adrenal cortex, showing numerous CD4-positive lymphocytes with strong positive staining of the cytoplasmic membrane; scored as grade 3 - IHC for CD4. (c) Same area, showing fewer CD8-positive lymphocytes; scored as grade 1 - IHC for CD8.

Figure 2

Primary hypoadrenocorticism, adrenal cortex, Dog 3. (a) Same area of cortex as in Figure 1, showing numerous CD4-positive lymphocytes; scored as grade 3 - ISH for CD4. (b) Same area, with only a few scattered CD8-positive lymphocytes; scored as grade 1 - ISH for CD8.

Figure 3

Semi-quantitative scoring of lymphocytic inflammation in the adrenal glands of five dogs with primary hypoadrenocorticism demonstrating a predominance of CD4+ cells. Adrenal gland sections were evaluated using IHC (left panel) and ISH (right panel) using antibodies (IHC) or probes (ISH) for CD4 and CD8, and the percentage of each cell type relative to the total number of lymphocytes was quantified on a scale of 0–3. CD4 staining is represented by circles and CD8 staining is represented by triangles; dashed lines connect the findings for each sample. A small amount of jitter was added to each point to permit visualization of overlapping values.