InVivoMAb anti-mouse/human KLRG-1

InVivoMAb anti-mouse/human KLRG-1 (CLONE: 2F1)

Togher, S., et al (2015). "FoxO3 is a negative regulator of primary CD8+ T-cell expansion but not of memory formation" Immunol Cell Biol 93(2): 120-125. PubMed

The generation of CD8(+) T cells by vaccination represents an important goal for protective immunity to infectious pathogens. It is thus of utmost importance to understand the mechanisms involved in the generation of optimal CD8(+) T-cell responses. The forkhead box O (FoxO) family of transcription factors has a crucial role in cellular responses to environmental change. Among them, FoxO3 is critically involved in the regulation of cellular proliferation, apoptosis, metabolism and stress resistance to withdrawal of nutrients or cytokine growth factors. Since the role of FoxO3 has been poorly studied in the immune system, here we have evaluated its involvement in the CD8(+) T-cell response. We observe that CD8(+) T cells deficient for FoxO3 undergo a significantly greater primary expansion than their wild-type (WT) counterparts in response to both infectious (vaccinia virus) or non-infectious (non-replicating cellular vaccine) immunogens, resulting in a larger cohort of cells following contraction. These survivors, however, do not undergo a greater secondary response than WT. Taken together, our data show that FoxO3 is a negative regulator of the CD8(+) T-cell response, specifically during the primary expansion.

Kim, M. H., et al (2015). "Retinoic Acid Differentially Regulates the Migration of Innate Lymphoid Cell Subsets to the Gut" Immunity 43(1): 107-119. PubMed

Distinct groups of innate lymphoid cells (ILCs) such as ILC1, ILC2, and ILC3 populate the intestine, but how these ILCs develop tissue tropism for this organ is unclear. We report that prior to migration to the intestine ILCs first undergo a “switch” in their expression of homing receptors from lymphoid to gut homing receptors. This process is regulated by mucosal dendritic cells and the gut-specific tissue factor retinoic acid (RA). This change in homing receptors is required for long-term population and effector function of ILCs in the intestine. Only ILC1 and ILC3, but not ILC2, undergo the RA-dependent homing receptor switch in gut-associated lymphoid tissues. In contrast, ILC2 acquire gut homing receptors in a largely RA-independent manner during their development in the bone marrow and can migrate directly to the intestine. Thus, distinct programs regulate the migration of ILC subsets to the intestine for regulation of innate immunity.

Becker, P. D., et al (2015). "Skin vaccination with live virus vectored microneedle arrays induce long lived CD8(+) T cell memory" Vaccine 33(37): 4691-4698. PubMed

A simple dissolvable microneedle array (MA) platform has emerged as a promising technology for vaccine delivery, due to needle-free injection with a formulation that preserves the immunogenicity of live viral vectored vaccines dried in the MA matrix. While recent studies have focused largely on design parameters optimized to induce primary CD8(+) T cell responses, the hallmark of a vaccine is synonymous with engendering long-lasting memory. Here, we address the capacity of dried MA vaccination to programme phenotypic markers indicative of effector/memory CD8(+) T cell subsets and also responsiveness to recall antigen benchmarked against conventional intradermal (ID) injection. We show that despite a slightly lower frequency of dividing T cell receptor transgenic CD8(+) T cells in secondary lymphoid tissue at an early time point, the absolute number of CD8(+) T cells expressing an effector memory (CD62L(-)CD127(+)) and central memory (CD62L(+)CD127(+)) phenotype during peak expansion were comparable after MA and ID vaccination with a recombinant human adenovirus type 5 vector (AdHu5) encoding HIV-1 gag. Similarly, both vaccination routes generated CD8(+) memory T cell subsets detected in draining LNs for at least two years post-vaccination capable of responding to secondary antigen. These data suggest that CD8(+) T cell effector/memory generation and long-term memory is largely unaffected by physical differences in vaccine delivery to the skin via dried MA or ID suspension.

Kastenmuller, W., et al (2011). "Regulatory T cells selectively control CD8+ T cell effector pool size via IL-2 restriction" J Immunol 187(6): 3186-3197. PubMed

Regulatory T cells (Treg) are key players in maintaining immune homeostasis but have also been shown to regulate immune responses against infectious pathogens. Therefore, Treg are a promising target for modulating immune responses to vaccines to improve their efficacy. Using a viral vector system, we found that Treg act on the developing immune response early postinfection by reducing the extent of dendritic cell costimulatory molecule expression. Due to this change and the lower IL-2 production that results, a substantial fraction of CD8(+) effector T cells lose CD25 expression several days after activation. Surprisingly, such Treg-dependent limitations in IL-2 signaling by Ag-activated CD8(+) T cells prevent effector differentiation without interfering with memory cell formation. In this way, Treg fine-tune the numbers of effector T cells generated while preserving the capacity for a rapid recall response upon pathogen re-exposure. This selective effect of Treg on a subpopulation of CD8(+) T cells indicates that although manipulation of the Treg compartment might not be optimal for prophylactic vaccinations, it can be potentially exploited to optimize vaccine efficacy for therapeutic interventions.

Mackerness, K. J., et al (2010). "Pronounced virus-dependent activation drives exhaustion but sustains IFN-gamma transcript levels" J Immunol 185(6): 3643-3651. PubMed

During many chronic infections, the responding CD8 T cells become exhausted as they progressively lose their ability to elaborate key effector functions. Unlike prototypic memory CD8 cells, which rapidly synthesize IFN-gamma following activation, severely exhausted T cells fail to produce this effector molecule. Nevertheless, the ontogeny of exhausted CD8 T cells, as well as the underlying mechanisms that account for their functional inactivation, remains ill defined. We have used cytokine reporter mice, which mark the transcription of IFN-gamma mRNA by the expression of Thy1.1, to decipher how activation events during the early stages of a chronic infection dictate the development of exhaustion. We show that virus-specific CD8 T cells clearly respond during the early stages of chronic lymphocytic choriomeningitis virus infection, and that this early T cell response is more pronounced than that initially observed in acutely infected hosts. Thus, exhausted CD8 T cells appear to emerge from populations of potently activated precursors. Unlike acute infections, which result in massive expansion of the responding T cells, there is a rapid attenuation of further expansion during chronic infections. The exhausted T cells that subsequently emerge in chronically infected hosts are incapable of producing the IFN-gamma protein. Surprisingly, high levels of the IFN-gamma transcript are still present in exhausted cells, demonstrating that ablation of IFN-gamma production by exhausted cells is not due to transcriptional silencing. Thus, posttranscription regulatory mechanisms likely disable this effector module.