Detection of human autoantibody against intercalated cells of kidney-collecting tubule.

Serum from a 24-year-old woman with a history of habitual abortions was examined for autoantibodies by indirect immunofluorescence microscopy. Fluorochrome-labelled antibodies to IgG revealed cytoplasmic staining of single cells in rat kidney collecting and connecting tubules. An identical staining pattern was reproducibly obtained in human and rabbit kidney, pointing to a cytoplasmic antigen concentrated in the apical pole of these cells. Lectin-binding histochemistry and immunohistochemical experiments using markers for different cell populations of the renal collecting tubule by double immunofluorescence technique, identified the cells recognized by the autoantibody as intercalated cells (ICC). Remarkably, this autoantibody reacted with a different antigen from those described to date in ICC, as evidenced by distribution and intracellular localization. The pattern of immunostaining suggests that all ICC are recognized in total rather than only one subpopulation. The connection between habitual abortions and this novel autoantibody are discussed.