Fine-needle aspiration biopsy in the monitoring of liver allografts. I. Correlation between aspiration biopsy and core biopsy in experimental pig liver allografts.

We have used allogeneic pig liver transplants to investigate the structure of inflammation in acute liver allograft rejection. An inflammatory episode of acute cellular rejection was observed in 9/10 allografts in nonimmunosuppressed recipients, when monitored with simultaneous fine-needle aspiration biopsies (FNAB) and core needle biopsies (NB). The intensity of inflammation in FNAB was quantitated using the corrected increment method and correlated with NB findings. In FNAB, all inflammatory episodes were detected on the 4th day after transplantation with lymphoid blast and lymphocyte infiltration, later accompanied by monocytes and macrophages. Maximal intensity of inflammation was recorded in FNAB on day 14. In NB, histology demonstrated distinct inflammation in the portal area on day 4. The predominantly lymphocytic infiltration, also containing varying numbers of plasma cells, eosinophils, neutrophils and macrophages, reached its maximum 7-14 days after transplantation. With the indirect immunoperoxidase technique, lymphoid cell subpopulation analysis of FNAB demonstrated an increase of both T4 and T8 cells during rejection. The T4/T8 ratio was first low, and increased at the beginning of the episode, on day 4, but decreased again on days 7 and 14. The number of B cells in the graft was also elevated during rejection. The cellular changes in the corresponding blood specimens followed approximately the same lines, although the changes were less prominent. NB immunohistology, using immunoperoxidase and frozen sections, correlated well with FNAB results, and demonstrated a T4 predominance in the portal area on day 4 but a T8 predominance on days 7 and 14. In addition to lymphoid cells, macrophages/granulocytes were also frequent in the portal area and scattered in the parenchyma on days 7 and 14. An additional inflammatory cell component in liver allograft rejection, detectable only in the NB, was eosinophils in the portal area, recorded in maximum on day 14. Taken together, the inflammatory changes in the FNAB and NB were similar, and time-related changes of cellular infiltrate in FNAB and NB correlated closely.