Lectin histochemistry and ultrastructure of rainbow trout Oncorhynchus mykiss kidneys affected by proliferative kidney disease

Eleven biotinylated lectins and the avidin-biotin-peroxidase system (ABC) were used to detect and localize specific carbohydrate residues of the primary (PKX-PCs) and daughter cells (PKK-DCs) of the PKX myxosporean, lymphocytes, macrophages and renal tubular epithelial cells of rainbow trout Oncorhynchus mykiss affected by proliferative kidney disease (PKD). Electron microscopy revealed the presence of the typical PKX-PCs and PKX-DCs in the renal interstitium, between tubular epithelial cells, and of some intraluminal forms, and showed that the principal inflammatory cells surrounding PKX were lymphocytes and macrophages. The latter were most often elongated and closely adherent to the PKX cell surface. The lectin PNA could be an important tool to evaluate the macrophage reaction during PKD and other infections of fishes. Finally, the elective staining of GS-I for PKX cells may be used in quantitative determinations by light microscopy of the degree of PKX infection, and for detection of the myxosporean when in low numbers. In addition, staining of PKX with lectins may allow recognition of forms of the parasites presently not well known, such as the early infective stages.