Multifunctional cytokine production marks influenza A virus‐specific CD4 T cells with high expression of survival molecules

Abstract

AbstractCytokine production by memory T cells is a key mechanism of T cell mediated protection. However, we have limited understanding of the persistence of cytokine producing T cells during memory cell maintenance and secondary responses. We interrogated antigen‐specific CD4 T cells using a mouse influenza A virus infection model. Although CD4 T cells detected using MHCII tetramers declined in lymphoid and non‐lymphoid organs, we found similar numbers of cytokine+ CD4 T cells at days 9 and 30 in the lymphoid organs. CD4 T cells with the capacity to produce cytokines expressed higher levels of pro‐survival molecules, CD127 and Bcl2, than non‐cytokine+ cells. Transcriptomic analysis revealed a heterogeneous population of memory CD4 T cells with three clusters of cytokine+ cells. These clusters match flow cytometry data and reveal an enhanced survival signature in cells capable of producing multiple cytokines. Following re‐infection, multifunctional T cells expressed low levels of the proliferation marker, Ki67, whereas cells that only produce the anti‐viral cytokine, interferon‐γ, were more likely to be Ki67+. Despite this, multifunctional memory T cells formed a substantial fraction of the secondary memory pool. Together these data indicate that survival rather than proliferation may dictate which populations persist within the memory pool.