Science: Incomplete B-cell tolerance in early childhoods in human fetuses facilitates the accumulation of multi-reactive B cells.

July 19, 2020 // --- it has long been known that the acquired immune system can produce a large pool of antibodies (immunoglobulins) in developing B cells through the recombination of the V(D) J geneExtensive immunoglobulin gene rearrangement allows humans to identify a variety of potential pathogensThis antibody bank (antibody repertoire, also translated as antibody spectrum) is subject to additional restrictions during early life to prevent the production of autologous reactive B cells, after all, tolerance does not seem to be completeIn addition, neonatal serum is rich in autoantibodies, which also suggests that B-cell tolerance during pregnancy has not yet been fully establishedB cells are the main pillarof our adaptive immune systemThey develop in the bone marrow and then circulate in the bloodB cells are responsible for producing antibodies against invasive pathogens (so-called antigens)Each B cell is highly specific to an antigenAntibodies are larger protein molecules called immunoglobulins that are secreted into the bloodstreamThey are also produced in the form of membrane binding and are present on the surface of B cells and are therefore called B-cell receptors (BCR)In a new study, researchers at Yale University and Rochester University in the United States assessed the reactive nature of more than 450 antibodies cloned from B cells in the human fetal liver, bone marrow and spleenThe findings, published in the July 17, 2020 issue of The Journal of Science, are entitled "Autoreactivity in na?ve human fetal B cells is es seis with commensal bacteria recognition"Photo from Science, 2020, doi: 10.1126/science.aay9733They found that incomplete early B-cell tolerance in human fetuses facilitates the accumulation of multi-reactive B cells, which can be combined with apoptosis and symbiotic bacteria from healthy adults without any somatic hypermutationsThese reactive B cells are produced before they come into contact with bacteria, which may promote later beneficial symbiotic-host interactions and/or enhance the host's defenses in the first week of lifeTherefore, a restricted fetal preimmune antibody bank contains potentially beneficial autoactive congenital B-cell specificity, which may help to remove apoptotic cells during development and promote the formation of the gut microbiome after birth(Bioon.com) References: Jeff W Chen et al Autoreactivity in na?ve human fetal B cells is associated with commensal bacteria recognition Science, 2020, doi: 10.1126/science.aay9733.