A rat model of monitoring liver allograft rejection.

Rat models are often used to study liver allograft rejection. We have established a model for rat liver allograft rejection, monitored by fine needle aspiration biopsy (FNAB), in the strain combination PVG-to-BN with a mean survival time of 37 +/- 20 days. In this model, we observed acute rejection with an intense peak of lymphoid blasts and lymphocyte-dominated inflammation in the FNAB [9.1 +/- 3.0 corrected increment units (CIU)], and an eventual increase in macrophages (up to 4.2 +/- 4.4 CIU), together with fibrosis and parenchymal necrosis in the graft. Markers of immune activation, such as an increase in IL-2-receptor (from 1% +/- 2% to 21% +/- 13%) and class II (from 20% +/- 9% to 43% +/- 13%) expressing lymphoid cells and induction of ICAM-1 in the graft, were consistent with the overall cellular response. The FNAB correlated well with parallel graft histology. In this rat model, the atraumatic monitoring makes a close follow-up possible without having to sacrifice the experimental animals. This saves work, animals, and costs in the study of liver rejection.