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English: The role of B cells in COVID-19 infection and re-infection. Naïve B cells are activated via the help of folliculat T (Tfh) cells after the invasion of SARS-CoV-2 virus. Following T-B interaction, B cells go through rapid proliferation and differentiation, producing pre-germinal center memory B cells (pre-GC MBCs) and short-lived plasma cells (SLPCs) producing early antibodies with low affinity. Other B cells enter the germinal center (GC) to increase antibody affinity by clonal expansion and somatic hypermutation (SHM), and change the structure through class-switching recombination (CSR), resulting in long-lived plasma cells (LLPCs) and memory B cells (MBCs). If challenged with a second invasion or vaccination, both pre-GC MBCs and MBCs generated after GC reactions differentiate into plasma cells or generate a second GC in a short period of time to produce high-affinity antibodies. Those B cells and antibodies secreted enter the blood circulation and peripheral tissues like mucosa to defend against viral infection and re-infection. Figure adapted from (18).