PD-1highCXCR5–CD4+ peripheral helper T cells promote CXCR3+ plasmablasts in human acute viral infection
Hiromitsu Asashima, Subhasis Mohanty, Michela Comi, William Ruff, Kenneth B. Hoehn, Patrick Wong, Jon Klein, Carolina Lucas, Inessa Cohen, Sarah Coffey, Nikhil Lele, Leissa Greta, Khadir Raddassi, Omkar Chaudhary, Avraham Unterman, Brinda Emu, Steven H. Kleinstein, Ruth R. Montgomery, Akiko Iwasaki, Charles S. Dela Cruz, Naftali Kaminski, Albert C. Shaw, David A. Hafler, Tomokazu S. Sumida
Abstract
T cell-B cell interaction is the key immune response to protect the host from severe viral infection. However, how T cells support B cells to exert protective humoral immunity in humans is not well understood. Here, we use COVID-19 as a model of acute viral infections and analyze CD4 + T cell subsets associated with plasmablast expansion and clinical outcome. Peripheral helper T cells (Tph cells; denoted as PD-1 high CXCR5 – CD4 + T cells) are significantly increased, as are plasmablasts. Tph cells exhibit "B cell help" signatures and induce plasmablast differentiation in vitro . Interestingly, expanded plasmablasts show increased CXCR3 expression, which is positively correlated with higher frequency of activated Tph cells and better clinical outcome. Mechanistically, Tph cells help B cell differentiation and produce more interferon γ (IFNγ), which induces CXCR3 expression on plasmablasts. These results elucidate a role for Tph cells in regulating protective B cell response during acute viral infection.