Explained: How different immune cells respond to Covid infection The team performed single-cell sequencing from 800,000 individual immune cells, along with detailed analysis of cell surface proteins Wednesday April 21, 2021 8:22 PM, IANS London: Researchers have identified differences in the immune response to Covid-19, between people with no symptoms, compared to those suffering a more serious reaction to the virus. The differences could help explain serious lung inflammation and blood clotting symptoms, and could be used to identify potential targets for developing therapies. The study, published in the journal Nature Medicine, found increased levels of B cells that produce antibodies that are found in mucus passages, such as the nose, in people with no symptoms.