Pre-transplant plasma and cellular levels of CD44 correlate with acute renal allograft rejection

Background. Since CD44 is involved in activation, proliferation, rolling and extravasation of lymphocytes, we hypothesized that it could be involved in the pathophysiology of acute renal allograft rejection. Methods. Plasma and peripheral blood mononuclear cells ( PBMCs) were collected from patients 24 h prior to transplantation and analysed retrospectively. Soluble CD44, interleukin-2 receptor ( IL-2R), intracellular adhesion molecule-1 ( ICAM-1) and C-reactive protein ( CRP) in plasma were determined by enzyme-linked immunosorbent assay ( ELISA). Cellular CD44 expression on peripheral lymphocytes was determined by flow cytometric analysis. Results. Patients who later developed renal allograft rejection had statistically significantly increased soluble CD44 levels, but not soluble ICAM-1, IL-2R or CRP in plasma prior to transplantation. In addition, cellular CD44 on T-lymphocytes was decreased 24 h prior to transplantation in patients that would reject their allograft, compared with patients without rejection. Additionally, plasma CD44 and cellular CD44 revealed an inversely proportional correlation. Lipopolysaccharide ( LPS)-induced immune activation did not influence plasma or cellular CD44 levels in healthy volunteers, suggesting that more specific factors influence the shedding of CD44 on T lymphocytes, leading to increased risk of renal allograft rejection. Conclusion. Although the exact mechanism remains to be elucidated and further research is required, soluble CD44 levels and cellular surface CD44 on T lymphocytes prior to transplantation might be useful as predictive markers for the occurrence of acute renal rejection