**2. Markers of nephrons damage**

After kidney transplantation it is particularly important to monitor the biomarkers which allow to detect progress in disease process and determine which functional parts of kidney are going to be damaged, to enable application of a quick appropriate treatment (Lisowska-Myjak, 2010; Alachkar et al., 2010; Metzger et al., 2010). Administration of immunosuppressants for preventing renal graft rejection may lead to progressive damage to the renal tissue (interstitial fibrosis, tubular micro calcifications, atrophy of renal tubules) caused by high toxicity of suppressing drugs. Cyclosporine A(CsA), tacrolimus, mycophenolate mofetil, basiliximab, prednizon and sirolimus (rapamycin) are commonly used in immunosuppressive therapy following kidney transplantation. Cyclosporine A and tacrolimus generate immunosuppres‐ sive action by binding to cyclofiline and inhibiting the action of calcineurin 2, which stimulates proliferation and differentiation of lymphocytes T. Cyclosporine A inhibits synthesis of lymphokines by lymphocytes T. Lymphokines synthesized by lymphocytes T stimulate immunological system and have the ability to "kill" inflammatory and neoplastic cells. Mycophenolate mofetil selectively inhibits inosine monophosphate dehydrogenase, a basic enzyme in guanosine synthesis. Mycophenolate mofetil inhibits proliferation of lymphocytes T and B after stimulation with antigenes, cytokines and mitogens. Basiliximab similarly to Daclizumab, blocks receptors for IL-2.

Majority of renal pathological changes concern glomerules, proximal and distal tubules as well as vascular endothelium. At first renal proximal tubular cells (Fig.1.) demonstrating highest metabolic activity, possessing high amounts of mitochondries, lysosomes and peroxysomes are damaged. Remaining sections of nephron such as: Henle's loop, distal tubules and collecting tubules are usually damaged later. There are numerous biomarkers that identify injury the area of the renal nephron, such as the glomerulus, the proximal, and the distal tubule.
