Expanded Antigen-Specific Elimination Assay to Measure Human CD8 T Cell Cytolytic Potential.

Durable cellular immunity against pathogens is dependent upon a coordinated recall response to antigen by memory CD8 T cells, involving their proliferation and the generation of secondary cytotoxic effector cells. Conventional assays measuring ex vivo cytotoxicity fail to capture this secondary cytolytic potential, especially in settings where cells have not been recently exposed to their cognate antigen in vivo. Here we describe the expanded antigen-specific elimination assay (EASEA), a flow cytometric endpoint assay to measure the capacity of human CD8 T cells to expand in vitro upon antigen re-exposure and generate secondary effector cells capable of selectively eliminating autologous antigen-pulsed target cells across a range of effector-to-target ratios.

Cytolytic CD8 T cells infiltrate germinal centers to limit ongoing HIV replication in spontaneous controller lymph nodes.

Follicular CD8 T cells (fCD8) mediate surveillance in lymph node (LN) germinal centers against lymphotropic infections and cancers, but the precise mechanisms by which these cells mediate immune control remain incompletely resolved. To address this, we investigated functionality, clonotypic compartmentalization, spatial localization, phenotypic characteristics, and transcriptional profiles of LN-resident virus-specific CD8 T cells in persons who control HIV without medications. Antigen-induced proliferative and cytolytic potential consistently distinguished spontaneous controllers from noncontrollers.

Functional impairment of HIV-specific CD8 T cells precedes aborted spontaneous control of viremia.

Spontaneous control of HIV infection has been repeatedly linked to antiviral CD8 T cells but is not always permanent. To address mechanisms of durable and aborted control of viremia, we evaluated immunologic and virologic parameters longitudinally among 34 HIV-infected subjects with differential outcomes. Despite sustained recognition of autologous virus, HIV-specific proliferative and cytolytic T cell effector functions became selectively and intrinsically impaired prior to aborted control.