Tamm-Horsfall protein in reflux nephropathy

Pyelonephritis in slaughter pigs and sows: morphological characterization and aspects of pathogenesis and aetiology

Background

Pyelonephritis is a serious disease in pig production that needs to be further studied. The purpose of this study was to describe the morphology, investigate the pathogenesis, and evaluate the aetiological role of Escherichia coli in pyelonephritis in slaughtered pigs by concurrent bacteriological, gross and histopathological examinations.

Methods

From Danish abattoirs, kidneys and corresponding lymph nodes from 22 slaughtered finishing pigs and 26 slaughtered sows with pyelonephritis were collected and evaluated by bacteriology and pathology. Based on gross lesions, each kidney (lesion) was grouped as acute, chronic, chronic active, or normal and their histological inflammatory stage was determined as normal (0), acute (1), sub-acute (2), chronic active (3), or chronic (4). Immunohistochemical identification of neutrophils, macrophages, T-lymphocytes, B-lymphocytes, plasma cells, E. coli and Tamm-Horsfall protein (THP) in renal sections was performed. The number of E. coli and the proportion of immunohistochemically visualized leukocytes out of the total number of infiltrating leukocytes were scored semi-quantitatively.

Results

Lesions in finishing pigs and sows were similar. Macroscopically, multiple unevenly distributed foci of inflammation mostly affecting the renal poles were observed. Histologically, tubulointerstitial infiltration with neutrophils and mononuclear cells and tubular destruction was the main findings. The significant highest scores of L1 antigen⁺ neutrophils were in inflammatory stage 1 while the significant highest scores of CD79αcy⁺ B-lymphocytes, IgG⁺ and IgA⁺ plasma cells were in stage 3 or 4. Neutrophils were the dominant leukocytes in stage 1 while CD3ε⁺ T-lymphocytes dominated in stage 2, 3 and 4. Interstitially THP was seen in 82% and 98% of kidneys with pyelonephritis from finishing pigs and sows, respectively. E. coli was demonstrated in monoculture and/or identified by immunohistochemistry in relation to inflammation in four kidneys from finishing pigs and in 34 kidneys from sows.

Conclusions

E. coli played a significant role in the aetiology of pyelonephritis. Neutrophils were involved in the first line of defence. CD3ε⁺ T-lymphocytes were involved in both the acute and chronic inflammatory response while a humoral immune response was most pronounced in later inflammatory stages. The observed renal lesions correspond with an ascending bacterial infection with presence of intra-renal reflux.

Intravenous Tamm-Horsfall protein polyps: report of a case in association with a hematoma that mimicked a renal neoplasm

Tamm-Horsfall protein (THP) is a glycoprotein produced only in the thick ascending limb of the loop of Henle. Its primary physiological function is unknown, but it may have a role in host defense against infectious organisms. THP is the primary scaffolding protein in all varieties of tubular casts. Under certain conditions, THP may be extruded from tubular lumens into the interstitium and lymphatic channels. It even may be found within lymph nodes sampled for staging of neoplastic conditions. THP deposits were described in lumens of large veins. The pathogenetic basis of this finding is not known, but obstruction of renal outflow was suggested, and several cases were associated with macroscopic hematuria. We report a case of intravenous THP polyposis in which, in addition to abundant hemorrhage, there was formation of a hematoma. This measured 12 cm in diameter and caused clinical concern for the possibility of renal cell carcinoma. Although the cause of the hematoma was not apparent, the association with striking intravenous polyps of THP is noteworthy because this represents the first association of intravenous THP polyps with a large intraparenchymal hematoma.

Interactions between renal tubules and interstitium

Renal tubules and interstitium have close physiological associations. Changes in both are often seen in renal disease. Damaged tubules can attract inflammatory cells and stimulate interstitial fibrosis, but do not always do so. Interstitial inflammation can damage tubules and can also stimulate fibrosis, and is probably always initiated by tubular events. Interstitial and tubular abnormalities are closely associated with changes in renal excretory function, but tubular events are more important. A main determinant of the outcome of renal disease is whether tubules can recover, not the extent of interstitial changes. If tubules are atrophic, they will not recover and renal function will be permanently impaired.