Immunisation against the mycobacterial heat shock protein (hsp-65) has been proposed to lead to production of autoantibodies against human lactoferrin. Such antibodies occur in ulcerative colitis and in primary sclerosing cholangitis. This study analysed the distribution of hsp-65 and lactoferrin in biopsy specimens from patients with inflammatory bowel disease and primary sclerosing cholangitis and studied whether immunisation against mycobacterial hsp-65 resulted in production of antilactoferrin antibodies and vice versa. Polyclonal rabbit antihuman lactoferrin and monoclonal mouse anti-hsp-65 (ML30) were used for immunohistochemistry on biopsy specimens from patients with inflammatory bowel disease and primary sclerosing cholangitis. Rats were immunised against human lactoferrin and mycobacterial hsp-65 respectively. Antibody measurements were done by enzyme immunosorbent assays. It was found that lactoferrin and hsp-60/65 were not codistributed. Lactoferrin was found on vascular endothelium and in nonparenchymal liver cells both in inflamed and uninflamed tissues, but only in the hepatocytes of inflamed liver. ML30 reactivity was not inhibited by antilactoferrin antibodies. Rat anti-hsp-65 serum had no detectable antilactoferrin antibodies. In conclusion, antilactoferrin antibodies probably do not arise by immunisation against mycobacterial hsp-65. Both nonparenchymal cells and hepatocytes probably participate in clearance of lactoferrin. Endothelial exposure of lactoferrin may have pathogenic implications in diseases with antilactoferrin autoantibodies.