Kupffer cells can present alloantigen in vitro: an effect abrogated by gadolinium

Portal venous (PV) injection of alloantigen can result in tolerance. We have previously reported that this effect is abrogated by pretreatment with gadolinium (Gd), an element known to inhibit Kupffer cell phagocytosis. To further elucidate the role of Kupffer cells (KC) in PV tolerance, the present study examined the ability of KC to present alloantigen in vitro to syngeneic responder lymphocytes after in vivo PV administration of alloantigen with or without pretreatment with Gd. Wistar Furth (WF) rats were pretreated 24 hr prior to KC harvest with a PV injection of 1 x 10(7) allogeneic Lewis (LEW) rat lymphocytes (KC-L) or saline (KC-N). Another group received Gd intravenously 24 h prior to the PV injection of LEW cells (KC-L + Gd). KC were isolated from the WF rats using collagenase digestion and Percoll (90% pure by morphologic criteria and by monoclonal antibodies KU-1 and ED-2). Responder WF lymphocytes were cocultured with media alone, or with KC as prepared above, for 72 hr. KC-L demonstrated significant stimulation of the WF responders (P = 0.02 vs KC-N). Gd abrogated this stimulation (P = 0.04, KC-L vs KC-L + Gd) but not by nonspecific inhibition of the cocultures (KC-N vs KC-L + Gd, P > 0.05, no difference). This study demonstrates that KC can effectively present PV alloantigen for the activation of naive syngeneic T lymphocytes, thereby further supporting the hypothesis that KC play an integral role in the induction of PV tolerance by presentation of antigen to responder T cells.