Interstitial mononuclear cell infiltration in Heymann nephritis

Interstitial mononuclear cell infiltration in rats during the development of autoimmune Heymann nephritis (HN) was studied using the fine-needle aspiration biopsy (FNAB) technique. The results were compared with those obtained by immunohistochemical studies of infiltrating T helper (T-h) and T suppressor/cytotoxic (T-s) cells, and with traditional histopathological and immunofluorescence examinations. Three weeks after initial immunization with isolated tubular brush border antigen, when the histopathological finding was quite normal, FNAB revealed increased numbers of interstitial blast cells, large granular lymphocytes and activated lymphocytes. These increases reached significant levels 2 weeks after a booster injection and were still prominent in a few rats with manifest membranous glomerulonephritis (MGN) and proteinuria 14 weeks after initial immunization. Immunohistochemical staining 3 weeks after immunization showed a significant increase in T-h cells in peritubular regions. Infiltration decreased successively 2 weeks after the booster and during manifest MGN. On the other hand, the mean number of cortically infiltrating T-s cells successively increased during the course of the study and this increase had reached a statistically significant level 2 weeks after the booster. Prominent T-s infiltration appeared in a few rats 2 weeks after the booster and when MGN was histopathologically manifest, and it was then associated with histopathologically detectable interstitial mononuclear infiltration and also with blast cell infiltration in FNAB. Our results suggest linkage between tubulointerstitial lesions in HN and cell-mediated immunoreactivity, and that severe interstitial inflammation is associated with T-s cell infiltration. Cytological interpretation indicated that infiltrating blast cells were plasmablasts, which may imply local antibody production, especially since anti-brush border antibody titres and blast cell infiltration simultaneously reached maximum levels 2 weeks after the booster.