Antibody injection in the egg yolk: maternal antibodies affect humoral immune response of the offspring

P>1. In vertebrate species, maternal antibodies specific for the pathogens to which mothers have been exposed can be transmitted to offspring before birth. This is assumed to be adaptive as these antibodies can be essential in protecting offspring early in life before their own immune system is fully developed. However, fitness consequences in natural conditions and the long-term effects of these mechanisms have yet to be fully examined. 2. Exploring the ecological and evolutionary implications of such maternal effects requires experimental manipulations to avoid potential confounding maternal effects. In birds, maternal antibodies are transmitted via the egg yolk - a self contained embryonic environment in which antibodies can be manipulated independently outside the maternal environment. 3. Here we use a novel technique to extract and experimentally manipulate maternal antibodies in the egg. Using the common quail (Coturnix coturnix), we demonstrate a blocking effect of antigen specific maternal antibodies received via egg injection, on the offspring's antibody response to an immune challenge with this antigen. Our results also suggest lower antibody production after a second immune challenge if maternal antibodies were present during first infection. 4. Maternal antibodies thus have the potential to affect the development of offspring immunity. Our innovative technique will enable further work to manipulate the transfer of maternal antibodies per se whilst controlling for confounding effects linked to maternal vaccination. Because it also enables to manipulate the amount of antibodies transferred, it will facilitate further study of their adaptive value and ecological consequences in natural host-parasite systems.