The production of
antibodies (Abs) in chickens and the extraction of specific Abs from egg yolk (
IgY Abs) are increasingly attracting the interest of the scientific community, as demonstrated by the significant growth of the
IgY literature. This review offers detailed and comprehensive information about
IgY-technology, including: a) possibilities for hen keeping in accordance with the Three Rs principles; b) new insights into the
IgY transfer mechanism from blood to yolk as a
biological basis for the technology; c) the comparative characteristics of
IgY Abs and
IgG Abs; d) the high efficacy of the technique, in view of the extraordinary amount of
IgY Ab produced by one hen in one year (between 20 g and 40 g
IgY in total); e) comparisons between the efficacies of
IgY Abs and
IgG Abs (rabbit, sheep, mouse) in several immunological assays; f) immunisation protocols, as well as the most commonly used
IgY-extraction procedures; g) new possibilities for application in human and veterinary medicine, including strategies for the treatment of Helicobacter pylori
infection or fatal
intestinal diseases in children, particularly in poor countries, for reducing the use of
antibiotics, and, in Asia and South America, for producing Abs against snake, spider and
scorpion venoms; and h) the use of
IgY Abs in various fields of research, also taking into consideration recent developments in South America (particularly Argentina and Cuba) and in Asia.