Getting together: dendritic cells, T cells, collaboration and fates

A centenary of service: 100 years of Immunology & Cell Biology

This year marks the 100th year of the publication of Immunology & Cell Biology since it was first published in March 1924 as the Australian Journal of Experimental Biology and Medical Science. In this Editorial, we recount the journal from its founding, to its focus on immunology, through to the modern era.

Neutrophil Cytosolic Factor 1 in Dendritic Cells Promotes Autoreactive CD8+ T Cell Activation via Cross-Presentation in Type 1 Diabetes

Aims: Reactive oxygen species (ROS) are critical in driving the onset of type 1 diabetes (T1D). Ablation of ROS derived from phagocytic NADPH oxidase 2 is protective against autoimmune diabetes in non-obese diabetic (NOD) mice. However, the mechanisms of NADPH oxidase 2-derived ROS in T1D pathogenesis need to be elucidated. Here, we have examined the role of Ncf1 (the regulatory subunit of NADPH oxidase 2) in dendritic cells (DC).

Results:Ncf1-mutant DCs exhibit reduced ability to activate autoreactive CD8⁺ T cells despite no difference in co-stimulatory molecule expression or pro-inflammatory cytokine production. When provided with exogenous whole-protein antigen, Ncf1-mutant NOD DCs showed strong phagosome acidification and rapid antigen degradation, which lead to an absence of protein translocation into the cytoplasm and deficient antigenic peptide loading on MHC Class I molecules.

Innovation: This study demonstrates that Ncf1 (p47^phox) is required for activation and effector function of CD8⁺ T cells by acting both intrinsically within the T cell as well as within professional antigen presenting cells.

Conclusion: ROS promote CD8⁺ T cell activation by facilitating autoantigen cross-presentation by DCs. ROS scavengers could potentially represent an important component of therapies aiming to disrupt autoantigen presentation and activation of CD8⁺ T cells in individuals at-risk for developing T1D.

Importance of EMT Factor ZEB1 in cDC1 "MutuDC Line" Mediated Induction of Th1 Immune Response

The role of Epithelial to Mesenchymal Transition (EMT) factor Zeb1 is well defined in metastasis and cancer progression but it's importance in dendritic cells (DCs) is unexplored until now. For the first time we report here that Zeb1 controls immunogenic responses of CD8α⁺ conventional Type-I (cDC1) DCs. We found that ZEB1 expression increases significantly after TLR9 stimulation and its depletion impairs activation, co-stimulation and secretion of important cytokines like IL-6, IL-10 and IL-12 in cDC1 MutuDC line. We further confirmed our findings in primary cDC1 DCs derived from bone marrow. Co-culture of these Zeb1 knock down (KD) DCs with OT-II CD4⁺ T helper cells skewed their differentiation toward Th2 subtype. Moreover, adoptive transfer of activated Zeb1 KD DCs cleared intestinal worms in helminth infected mice by increasing Th2 responses in vivo. Integrative genomic analysis showed Zeb1 as an activator of immune response genes in cDC1 MutuDCs as compared to other pathway genes. In addition, differentially regulated genes in Zeb1 KD RNA-seq showed significant enrichment of Th2 activation pathways supporting our in vitro findings. Mechanistically, we showed that decreased IL-12 secreted by Zeb1 KD DCs is the plausible mechanism for increased Th2 differentiation. Collectively our data demonstrate that Zeb1 could be targeted in DCs to modulate T-cell mediated adaptive immune responses.

Collateral Damage: What Effect Does Anti-CD4 and Anti-CD8α Antibody-Mediated Depletion Have on Leukocyte Populations?

Anti-CD4 or anti-CD8α Ab-mediated depletion strategies are widely used to determine the role of T cell subsets. However, surface expression of CD4 and CD8α is not limited to T cells and occurs on other leukocyte populations as well. Using both unbiased t-distributed stochastic neighbor embedding of flow cytometry data and conventional gating strategies, we assessed the impact of anti-CD4 and anti-CD8α Ab-mediated depletion on non-T cell populations in mice. Our results show that anti-CD4 and anti-CD8α Ab injections not only resulted in depletion of T cells but also led to depletion of specific dendritic cell subsets in a dose-dependent manner. Importantly, the extent of this effect varied between mock- and virus-infected mice. We also demonstrate the importance of using a second, noncompeting Ab (clone CT-CD8α) to detect CD8α⁺ cells following depletion with anti-CD8α Ab clone 2.43. Our study provides a necessary caution to carefully consider the effects on nontarget cells when using Ab injections for leukocyte depletion in all experimental conditions.

Developing effective vaccines: Cues from natural infection

The ultimate goal of any vaccine is to generate a heterogeneous and stable pool of memory lymphocytes. Vaccine are designed with the hope to generate antigen specific long-lived T cell responses, as it may be the case in natural infection; however, inducing such response by sub-unit vaccine has been a challenge. Although significant progress has been made, there is lot of scope for designing novel vaccine strategies by taking cues from the natural infection. This review focuses upon the roadblocks and the possible ways to overcome them leading to developing effective vaccines. Here we propose that mimicking the natural course of infection as well as the inclusion of non-target antigens in vaccine formulations might generate heterogeneous pool of memory T cells to ensure long-lived protection.

T-cell intrinsic and extrinsic mechanisms of p27Kip1 in the regulation of CD8 T-cell memory

CD8 T cells exhibit dynamic alterations in proliferation and apoptosis during various phases of the CD8 T cell response, but the mechanisms that regulate cellular proliferation from the standpoint of CD8 T cell memory are not well defined. The cyclin-dependent kinase inhibitor p27^Kip1 functions as a negative regulator of the cell cycle in various cell types including T cells and it has been implicated in regulating cellular processes including differentiation, transcription and migration. Here, we investigated whether p27^Kip1 regulates CD8 T cell memory by T cell-intrinsic or T cell-extrinsic mechanisms, by conditional ablation of p27^Kip1 in T cells or non-T cells. Studies of T cell responses to an acute viral infection show that p27^Kip1 negatively regulates the proliferation of CD8 T cells by T cell-intrinsic mechanisms. However, the enhanced proliferation of CD8 T cells induced by T cell-specific p27^Kip1 deficiency minimally affects the primary expansion or the magnitude of CD8 T cell memory. Unexpectedly, p27^Kip1 ablation in non-T cells markedly augmented the number of high quality memory CD8 T cells by enhancing the accumulation of memory precursor effector cells without increasing their proliferation. Further studies show that p27^Kip1 deficiency in immunizing DCs fail to enhance CD8 T cell memory. Nevertheless, we have delineated the T cell-intrinsic, anti-proliferative activities of p27^Kip1 in CD8 T cells from its role as a factor in non-T cells that restricts the development of CD8 T cell memory. These findings have implications in vaccine development and understanding the mechanisms that maintain T cell homeostasis.

Immunotherapy for cancer: synthetic carbohydrate-based vaccines

Aberrant glycosylation of glycoproteins and glycolipids of cancer cells, which correlates with poor survival rates, is being exploited for the development of immunotherapies for cancer. In particular, advances in the knowledge of cooperation between the innate and adaptive system combined with the implementation of efficient synthetic methods for assembly of oligosaccharides and glycopeptides is providing avenues for the rationale design of vaccine candidates. In this respect, fully synthetic vaccine candidates show great promise because they incorporate only those elements requires for relevant immune responses, and hence do not suffer from immune suppression observed with classical carbohydrate-protein conjugate vaccines. Such vaccines are chemically well-defined and it is to be expected that they can be produced in a reproducible fashion. In this feature article, recent advances in the development of fully synthetic sub-unit carbohydrate-based cancer vaccines will be discussed.