In genetically-related donation the concept of non-inherited HLA antigens is worthy of a brief description. We have above described the role of the inherited maternal and paternal HLA haplotypes, which can also be referred to as the inherited maternal antigens and the inherited paternal antigens. But the effect of the so-called non-inherited maternal antigens is of academic interest and clinical relevance in certain scenarios. Non-inhereted maternal antigens consist of the HLA alleles present in the maternal haplotype non-inherited to a given child but to which the immune system of that child was exposed during foetal development and potentially developed tolerance. Because of this, transplants derived from mothers are less immunogenic than from fathers, and transplants performed between siblings when the mismatched haplotype is part of the non-inherited maternal antigens do better than when mismatched antigens derive from the non-inherited paternal antigens.