Background: Humoral immunity requires interaction between B cell and T follicular helper cells (Tfh) to produce effective immune response, but the data regarding a role of B cells and Tfh in SARS-CoV-2 defense are still sparse.
Methods: Blood samples from patients with acute COVID-19 (n = 64), convalescents patients who had specific IgG to SARS-CoV-2 N-protein (n = 55), and healthy donors with no detectable antibodies to any SARS-CoV-2 proteins (HC, n = 44) were analyses by multicolor flow cytometry.
Results: Patients with acute COVID-19 showed decreased levels of memory B cells subsets and increased proportion plasma cell precursors compared to HC and COVID-19 convalescent patients, whereas for the latter the elevated numbers of virgin naïve, Bm2' and "Bm3+Bm4" was found if compared with HC. During acute COVID-19 CXCR3+CCR6- Tfh1-like cells were decreased and the levels of CXCR3-CCR6+ Tfh17-like were increased then in HC and convalescent patients. Finally, COVID-19 convalescent patients had increased levels of Tfh2-, Tfh17- and DP Tfh-like cells while comparing their amount with HC.
Conclusions: Our data indicate that COVID-19 can impact the humoral immunity in the long-term.
Keywords: B cell subsets; COVID-19; SARS-CoV-2; T follicular helper cells; Tfh cell subsets; convalescents.