Lamarckian inheritance by somatically acquired maternal IgG phenotypes

Maternal antibodies provide offspring with passive immunity and exert various active immunostimulatory functions, such as (i) antimicrobial protection through non-antigen-reactive antibodies, namely anti-idiotypes, (ii) allergen-specific suppression of IgE responsiveness and (iii) under pathological conditions, transfer of autoimmune diseases. As products of mainly T cell-dependent immune responses with long-lived antigen-independent plasma cells, maternal IgG molecules have undergone immune maturation by somatic hypermutations and are therefore acquired immunological phenotypes representing the collective immunological experience of the mother. The inductive function of maternal IgG, although limited to a neonatal imprinting period, exerts a life-long determinative influence, which can dominate over seemingly genetic predispositions. Hence, the functional impact of maternal IgG in offspring appears phenotypically as a non-genetic inheritance, which thus reveals a Lamarckian dimension of the immune system.