Mannan-binding protein in human liver.

Mannan-binding protein (MBP) is a Ca(2+)-dependent lectin which was first described in 1978 in rabbit liver, and subsequently in serum and liver tissue from humans and a range of animal species. MBP structurally resembles C1q, and may act both as a focus for complement activation on the surface of microorganisms and as an opsonin in its own right. Low serum levels of serum MBP have been described in a group of children known to suffer from severe recurrent infections. MBP has also been reported to behave as an acute phase reactant. This preliminary study has investigated the localisation of MBP in human tissues using material obtained both at post mortem and from diagnostic liver biopsies. Using the IgG fraction of rabbit anti-human MBP, immunoperoxidase staining showed no evidence of significant MBP in a wide range of normal tissues, including liver taken both at post mortem and needle biopsy. However, there was a significant degree of staining for MBP in liver biopsies showing a variety of different pathologies, in particular severely damaged alcoholic livers, and those harbouring metastatic tumour. Moderate degrees of staining were also seen in liver biopsies from patients suffering from chronic biliary disease. It is uncertain whether this localisation of MBP in abnormal liver is an acute phase response, or represents a more fundamental link with liver disease. This question could be the focus for future studies.