Washington – Researchers at Washington University in St. Louis, US, have found that during a viral infection, antibody-producing immune cells rapidly multiply and circulate in the blood, driving antibody levels sky-high. A small population of antibody-producing cells, called long-lived plasma cells, migrate to the bone marrow and settle in, where they continually secrete low levels of antibodies into the bloodstream to help guard against another encounter with the virus. Ali Ellebedy, Associate Professor at the varsity’s School of Medicine, said: “We found antibody-producing cells in people 11 months after the first symptoms. These cells will live and produce antibodies for the rest of people’s lives. That’s strong evidence for long-lasting immunity.” The team obtained bone marrow from 18 of the participants seven or eight months after their initial infections. For comparison, the scientists also obtained bone marrow from 11 people who had never had Covid-19. Of the bone marrow samples, 15 contained antibody-producing cells specifically targeting the virus that causes Covid-19. Such cells could still be found four months later in the five people who came back to provide a second bone-marrow sample. None of the 11 people who had never had Covid-19 had such antibody-producing cells in their bone marrow.