MKI67 and COVID-19: Interestingly, these cells formed a male sex-biased hub with additional strong correlations to plasma cells, proliferating (Ki67+) memory B cells, and CD11c+CXCR5− extrafollicular/atypical B cells (Fig. 6C), of which the latter have previously been suggested to be driven by Tph in the context of autoimmunity (43) and appear to be a major source of neutralizing antibodies in COVID-19 (39).