CD39 Is Expressed on Functional Effector and Tissue-resident Memory CD8+ T Cells.

The ecto-ATPase CD39 is expressed on exhausted CD8+ T cells in chronic viral infection and has been proposed as a marker of tumor-specific CD8+ T cells in cancer, but the role of CD39 in an effector and memory T cell response has not been clearly defined. We report that CD39 is expressed on Ag-specific CD8+ short-lived effector cells, while it's co-ectoenzyme, CD73, is found on memory precursor effector cells (MPECs) in vivo. Inhibition of CD39 enzymatic activity during in vitro T cell priming enhances MPEC differentiation in vivo after transfer and infection. The enriched MPEC phenotype is associated with enhanced tissue resident memory T cell (TRM cell) establishment in the brain and salivary gland following an acute intranasal viral infection, suggesting that CD39 ATPase activity plays a role in memory CD8+ T cell differentiation. We also show that CD39 is expressed on human and murine TRM cells across several nonlymphoid tissues and melanoma, whereas CD73 is expressed on both circulating and resident memory subsets in mice. In contrast to exhausted CD39+ T cells in chronic infection, CD39+ TRM cells are fully functional when stimulated ex vivo with cognate Ag, further expanding the identity of CD39 beyond a T cell exhaustion marker.

Validation of Ligand Tetramers for the Detection of Antigen-Specific Lymphocytes.

The study of Ag-specific lymphocytes has been a key advancement in immunology over the past few decades. The development of multimerized probes containing Ags, peptide:MHC complexes, or other ligands was one innovation allowing the direct study of Ag-specific lymphocytes by flow cytometry. Although these types of study are now common and performed by thousands of laboratories, quality control and assessment of probe quality are often minimal. In fact, many of these types of probe are made in-house, and protocols vary between laboratories. Although peptide:MHC multimers can often be obtained from commercial sources or core facilities, few such services exist for Ag multimers. To ensure high quality and consistency with ligand probes, we have developed an easy and robust multiplexed approach using commercially available beads able to bind Abs specific for the ligand of interest. Using this assay, we have sensitively assessed the performance of peptide:MHC and Ag tetramers and have found considerable batch-to-batch variability in performance and stability over time more easily than using murine or human cell-based assays. This bead-based assay can also reveal common production errors such as miscalculation of Ag concentration. This work could set the stage for the development of standardized assays for all commonly used ligand probes to limit laboratory-to-laboratory technical variation and experimental failure caused by probe underperformance.

Nasal and pharyngeal mucosal immunity to poliovirus in children following routine immunization with inactivated polio vaccine (IPV) in the United States of America.

BACKGROUND: Although polioviruses (PVs) replicate in lymphoid tissue of both the pharynx and ileum, research on polio vaccine-induced mucosal immunity has predominantly focused on intestinal neutralizing and binding antibody levels measured in stool. METHODS: To investigate the extent to which routine immunization with intramuscularly injected inactivated polio vaccine (IPV) may induce nasal and pharyngeal mucosal immunity, we measured PV type-specific neutralization and immunoglobulin (Ig) G, IgA, and IgM levels in nasal secretions, adenoid cell supernatants, and sera collected from 12 children, aged 2 to 5 years, undergoing planned adenoidectomies. All participants were routinely immunized with IPV and had no known contact with live PVs. RESULTS: PV-specific mucosal neutralization was detected in nasal and adenoid samples, mostly from children who had previously received four IPV doses. Across the three PV serotypes, both nasal (Spearman's rho ≥ 0.87, p≤0.0003 for all) and adenoid (Spearman's rho ≥0.57, p≤0.05 for all) neutralization titers correlated with serum neutralization titers. In this small study sample, there was insufficient evidence to determine which Ig isotype(s) was correlated with neutralization. CONCLUSIONS: Our findings provide policy-relevant evidence that routine immunization with IPV may induce nasal and pharyngeal mucosal immunity. The observed correlations of nasal and pharyngeal mucosal neutralization with serum neutralization contrast with previous observations of distinct intestinal and serum responses to PV vaccines. Further research is warranted to determine which antibody isotype(s) correlate with polio vaccine-induced nasal and pharyngeal mucosal neutralizing activity and to understand the differences from intestinal mucosal immunity.

Alarm functions of PD-1+ brain resident memory T cells.

Resident memory T cells (T RM ) have been described in barrier tissues as having a 'sensing and alarm' function where, upon sensing cognate antigen, they alarm the surrounding tissue and orchestrate local recruitment and activation of immune cells. In the immunologically unique and tightly restricted CNS, it remains unclear if and how brain T RM , which express the inhibitory receptor PD-1, alarm the surrounding tissue during antigen re-encounter. Here, we reveal that T RM are sufficient to drive the rapid remodeling of the brain immune landscape through activation of microglia, DCs, NK cells, and B cells, expansion of Tregs, and recruitment of macrophages and monocytic dendritic cells. Moreover, we report that while PD-1 restrains granzyme B expression by reactivated brain T RM , it has no effect on cytotoxicity or downstream alarm responses. We conclude that T RM are sufficient to trigger rapid immune activation and recruitment in the CNS and may have an unappreciated role in driving neuroinflammation.

CD39 is expressed on functional effector and tissue resident memory CD8+ T cells.

The ecto-ATPase CD39 is expressed on exhausted CD8+ T cells in chronic viral infection and has been proposed as a marker of tumor-specific CD8+ T cells in cancer, but the role of CD39 in an effector and memory T cell response has not been clearly defined. We report that CD39 is expressed on antigen-specific CD8+ short-lived effector cells (SLECs), while it's co-ecto-enzyme, CD73, is found on memory precursor effector cells (MPEC) in vivo . Inhibition of CD39 enzymatic activity during in vitro T cell priming enhances MPEC differentiation in vivo after transfer and infection. The enriched MPEC phenotype is associated with enhanced tissue resident memory (T RM ) establishment in the brain and salivary gland following an acute intranasal viral infection, suggesting that CD39 ATPase activity plays a role in memory CD8+ T cell differentiation. We also show that CD39 is expressed on human and murine T RM across several non-lymphoid tissues and melanoma, while CD73 is expressed on both circulating and resident memory subsets in mice. In contrast to exhausted CD39+ T cells in chronic infection, CD39+ T RM are fully functional when stimulated ex vivo with cognate antigen. This work further expands the identity of CD39 beyond a T cell exhaustion marker.

Tissue-resident memory T cells trigger rapid exudation and local antibody accumulation.

Adaptive immunity is didactically partitioned into humoral and cell-mediated effector mechanisms, which may imply that each arm is separate and does not function together. Here, we report that the activation of CD8+ resident memory T cells (TRM) in nonlymphoid tissues triggers vascular permeability, which facilitates rapid distribution of serum antibodies into local tissues. TRM reactivation was associated with transcriptional upregulation of antiviral signaling pathways as well as Fc receptors and components of the complement cascade. Effects were local, but evidence is presented that TRM in brain and reproductive mucosa are both competent to induce rapid antibody exudation. TRM reactivation in the mouse female genital tract increased local concentrations of virus-specific neutralizing antibodies, including anti-vesicular stomatitis virus, and passively transferred anti-HIV antibodies. We showed that this response was sufficient to increase the efficacy of ex vivo vesicular stomatitis virus neutralization. These results indicate that CD8+ TRM antigen recognition can enhance local humoral immunity.