CD79A and COVID-19: Nevertheless, many of the same proteins were the most differentially reactive with COVID-19 patient serum IgA compared to healthy donor serum IgA, including the N and S proteins and RBD of SARS-CoV-2 as well as the N, S, and M proteins of SARS-CoV with t test P values ranging from 2.1 × 10−6 to 1.1 × 10−3 (Fig. S4).