Immunofluorescence is the mainstay among immunohistochemical techniques used in identifying the immunopathogenesis of renal disease. Enzyme-conjugated antibodies helpful in electron microscopy have note yet found wide use in light microscopy. Immunological renal injury may follw, first, if antibodies react with the renal basement membranes, either glomerular or tubular (GBM, TBM), and second, if antibodies combine with nonglomerular antigens in the circulation to form nephritogenic immune complexes that lodge in the glomerular filter or renal interstitium. With immunofluorescence, one can then identify these antibody deposite which initiate renal injury. Since anti-GBM or anti-TBM, antibodies react all along the GBM or TBM, they appear as smooth linear deposits of immunoglobulin(Ig). Immune complexes depositing at random in the renal vasculature, predominantly the glomeruli, produce a granular, irregular accumulation of Ig. Either type of antibody reaction in the kidney can lead to activation of mediators of immunological injury, such as complement, which can also be characterized by immunofluorescence.
Satisfactory immunofluorescence study requires adequate tissue sections, optimal fluorescent-antibody reagents, adequate fluorescence microscopic equipment, and a good deal of experience in interpreting the findings. Portions of this part are directed toward each of these pointes, and a detailed description of tissue processing, fixation, and staining is included.
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