Along with inducing antibodies for immediate defense, mRNA vaccines against COVID-19 also stimulate the lymph nodes to generate immune cells that provide protection over the long term, a new study confirms. The early wave of antibodies are generated by B cells called plasmablasts. In healthy volunteers, blood tests showed that two doses of the Pfizer/BioNTech vaccine induced "a strong plasmablast response," said coauthor Ali Ellebedy of Washington University School of Medicine in St. Louis. The memory B cells that will produce antibodies upon exposure to the virus in years to come are generated by germinal center B cells found only in lymph nodes near vaccine injection sites, his team explained in a paper currently undergoing peer review for possible publication in a Nature journal. In repeated biopsies of volunteers' lymph nodes, "we saw a robust germinal center response," Ellebedy said. The responses lasted at least seven weeks, "with no sign of cooling down anytime soon," he added. "While we do not have long-term samples yet, it is safe to assume given the magnitude and persistence of the germinal center reaction that those individuals will develop a durable immune response" to mRNA vaccines. COVID-19 vaccines from Arcturus Therapeutics, CureVac, and Moderna Inc. also use mRNA technology. —Reuters Staff Source
