Spatiotemporal resolution of germinal center Tfh cell differentiation and divergence from central memory CD4 T cell fate.

Follicular helper T (Tfh) cells are essential for germinal center (GC) B cell responses. However, it is not clear which PD-1CXCR5Bcl6CD4 T cells will differentiate into PD-1CXCR5Bcl6 GC-Tfh cells and how GC-Tfh cell differentiation is regulated. Here, we report that the sustained Tigit expression in PD-1CXCR5CD4 T cells marks the precursor Tfh (pre-Tfh) to GC-Tfh transition, whereas TigitPD-1CXCR5CD4 T cells upregulate IL-7Rα to become CXCR5CD4 T memory cells with or without CCR7.

Lentiviral Nef Proteins Differentially Govern the Establishment of Viral Latency.

Despite the clinical importance of latent human immunodeficiency virus type 1 (HIV-1) infection, our understanding of the biomolecular processes involved in HIV-1 latency control is still limited. This study was designed to address whether interactions between viral proteins, specifically HIV Nef, and the host cell could affect latency establishment. The study was driven by three reported observations.

Host T Cell Dedifferentiation Effects Drive HIV-1 Latency Stability.

The development of therapies to eliminate the latent HIV-1 reservoir is hampered by our incomplete understanding of the biomolecular mechanism governing HIV-1 latency. To further complicate matters, recent single-cell RNA sequencing (scRNA-seq) studies reported extensive heterogeneity between latently HIV-1-infected primary T cells, implying that latent HIV-1 infection can persist in greatly differing host cell environments. We show here that transcriptomic heterogeneity is also found between latently infected T cell lines, which allowed us to study the underlying mechanisms of intercell heterogeneity at high signal resolution.

Extensive proteomic and transcriptomic changes quench the TCR/CD3 activation signal of latently HIV-1 infected T cells.

The biomolecular mechanisms controlling latent HIV-1 infection, despite their importance for the development of a cure for HIV-1 infection, are only partially understood. For example, ex vivo studies have recently shown that T cell activation only triggered HIV-1 reactivation in a fraction of the latently infected CD4+ T cell reservoir, but the molecular biology of this phenomenon is unclear. We demonstrate that HIV-1 infection of primary T cells and T cell lines indeed generates a substantial amount of T cell receptor (TCR)/CD3 activation-inert latently infected T cells.

Bach2 Negatively Regulates T Follicular Helper Cell Differentiation and Is Critical for CD4 T Cell Memory.

T follicular helper (Tfh) cells are essential for germinal center B cell responses. The molecular mechanism underlying the initial Tfh cell differentiation, however, is still incompletely understood. In this study, we show that in vivo, despite enhanced non-Tfh cell effector functions, the deletion of transcription factor Bach2 results in preferential Tfh cell differentiation.