Fig. 1

Schematic drawing of the normal (left) versus immunopathogenic (right) transfer of antibodies from the mother to the fetus. Normally, maternal antibodies of the IgG class cross the placenta (box 1) from 17 to 22 week’s gestational age. This passive transfer of immunity does not initiate an immune response by the maternal antibodies towards fetal antigens, but provides the fetus with humoral immunity (box 2) to protect against infectious agents. The alloimmune hypothesis behind neonatal haemochromatosis (NH) involves the maternal exposure to a yet unknown fetal liver antigen, followed by the production of antibodies of the IgG class towards this antigen (circle 1). These antigens then cross the placenta, and enter fetal circulation (circle 2). Binding of these antibodies to the antigen on the fetal liver (circle 3) activates the terminal complement cascade, and the assembly of membrane attack complex, which causes hepatocyte lysis. This liver damage may appear as an acute hepatitis in some NH cases, or more commonly as a chronic/subacute hepatitis