Methods of monitoring and detecting the early onset of organ injury incident rejection of a organ rejection in an animal are disclosed. The described methods are capable of distinguishing organ rejection injury from other organ tissue damage in the animal. Free secretory component levels in an animal biological fluid (e.g., bile, urine, blood, amniotic fluid) may be used to identify organ rejection in an animal. Multiple and single organ transplant patients may be monitored and diagnosed according to the claimed methods. Biological fluids, such as blood, (serum) or urine, are analyzed immunologically using a particularly adapted ELISA which are then compared to an FSC control concentration to identify elevated FSC values. Animals with test FSC above FSC control concentrations are diagnosed as having an ongoing organ rejection episode. The detection of congenital renal dysfunction in utero is also provided according to the present invention through the measurement of FSC in the amniotic fluid. The described methods are specific for indicating organ rejection tissue injury, and distinguish kidney rejection tissue injury, in particular, from other causes of kidney injury, such as cyclosporin toxicity, urinary tract infection, and urinary obstruction and toxicity (incident to immunosuppressive therapy with cyclosporin). A kit for use in the identification of an organ rejection episode in a patient through measurement of FSC in a biological sample is also provided.Board of Regents, University of Texas Syste
