Importantly, upon comparison of unswitched to switched memory B cells from severe SARS-CoV-2 infection, unswitched memory B cells express higher levels of pSYK and pPLCγ2 after BCR stimulation than switched memory B cells (Figure 5C), (which was surprising given higher expression of inhibitory receptors CD72 and CD22 on unswitched memory B cells) demonstrating that unswitched memory B cells are better poised to respond to antigen recognition than switched memory B cells during severe viral infection. This evidence concerns the gene CD72 and viral infectious disease.