Autophagy in T cells from aged donors is maintained by spermidine and correlates with function and vaccine responses

Vaccines are powerful tools to develop immune memory to infectious diseases and prevent excess mortality. In older adults, however vaccines are generally less efficacious and the molecular mechanisms that underpin this remain largely unknown. Autophagy, a process known to prevent aging, is critical for the maintenance of immune memory in mice. Here, we show that autophagy is specifically induced in vaccine-induced antigen-specific CD8+ T cells in healthy human volunteers. In addition, reduced IFNγ secretion by RSV-induced T cells in older vaccinees correlates with low autophagy levels. We demonstrate that levels of the endogenous autophagy-inducing metabolite spermidine fall in human T cells with age. Spermidine supplementation in T cells from old donors recovers their autophagy level and function, similar to young donors' cells, in which spermidine biosynthesis has been inhibited. Finally, our data show that endogenous spermidine maintains autophagy via the translation factor eIF5A and transcription factor TFEB. In summary, we have provided evidence for the importance of autophagy in vaccine immunogenicity in older humans and uncovered two novel drug targets that may increase vaccination efficiency in the aging context.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Superoxide Dismutase 1 Protects Hepatocytes from Type I Interferon-Driven Oxidative Damage

Tissue damage caused by viral hepatitis is a major cause of morbidity and mortality worldwide. Using a mouse model of viral hepatitis, we identified virus-induced early transcriptional changes in the redox pathways in the liver, including downregulation of superoxide dismutase 1 (Sod1). Sod1(-/-) mice exhibited increased inflammation and aggravated liver damage upon viral infection, which was independent of T and NK cells and could be ameliorated by antioxidant treatment. Type I interferon (IFN-I) led to a downregulation of Sod1 and caused oxidative liver damage in Sod1(-/-) and wild-type mice. Genetic and pharmacological ablation of the IFN-I signaling pathway protected against virus-induced liver damage. These results delineate IFN-I mediated oxidative stress as a key mediator of virus-induced liver damage and describe a mechanism of innate-immunity-driven pathology, linking IFN-I signaling with antioxidant host defense and infection-associated tissue damage. VIDEO ABSTRACT.

Autophagy Controls Acquisition of Aging Features in Macrophages

Macrophages provide a bridge linking innate and adaptive immunity. An increased frequency of macrophages and other myeloid cells paired with excessive cytokine production is commonly seen in the aging immune system, known as 'inflamm-aging'. It is presently unclear how healthy macrophages are maintained throughout life and what connects inflammation with myeloid dysfunction during aging. Autophagy, an intracellular degradation mechanism, has known links with aging and lifespan extension. Here, we show for the first time that autophagy regulates the acquisition of major aging features in macrophages. In the absence of the essential autophagy gene Atg7, macrophage populations are increased and key functions such as phagocytosis and nitrite burst are reduced, while the inflammatory cytokine response is significantly increased - a phenotype also observed in aged macrophages. Furthermore, reduced autophagy decreases surface antigen expression and skews macrophage metabolism toward glycolysis. We show that macrophages from aged mice exhibit significantly reduced autophagic flux compared to young mice. These data demonstrate that autophagy plays a critical role in the maintenance of macrophage homeostasis and function, regulating inflammation and metabolism and thereby preventing immunosenescence. Thus, autophagy modulation may prevent excess inflammation and preserve macrophage function during aging, improving immune responses and reducing the morbidity and mortality associated with inflamm-aging.

Autophagy is a critical regulator of memory CD8(+) T cell formation

During infection, CD8⁺ T cells initially expand then contract, leaving a small memory pool providing long lasting immunity. While it has been described that CD8⁺ T cell memory formation becomes defective in old age, the cellular mechanism is largely unknown. Autophagy is a major cellular lysosomal degradation pathway of bulk material, and levels are known to fall with age. In this study, we describe a novel role for autophagy in CD8⁺ T cell memory formation. Mice lacking the autophagy gene Atg7 in T cells failed to establish CD8⁺ T cell memory to influenza and MCMV infection. Interestingly, autophagy levels were diminished in CD8⁺ T cells from aged mice. We could rejuvenate CD8⁺ T cell responses in elderly mice in an autophagy dependent manner using the compound spermidine. This study reveals a cell intrinsic explanation for poor CD8⁺ T cell memory in the elderly and potentially offers novel immune modulators to improve aged immunity.

DOI:http://dx.doi.org/10.7554/eLife.03706.001

In the face of an infection, the immune system mounts an aggressive response by producing many copies of killer immune cells called CD8⁺ T cells that recognize and destroy any cells infected with the invading pathogen. The number of killer cells produced depends on the extent of the infection. Once the infection has been brought under control, most of the CD8⁺ T cells die off. The small numbers that are retained—called memory cells—‘remember’ the pathogen, so that if it invades the body again, they can help the immune system to respond more quickly and effectively.

Memory cells are also critical to the effectiveness of vaccines, many of which introduce a dead or weakened pathogen into the body. This does not cause an infection, but does allow the immune system to create memory cells that are able to fend off the same pathogen in the future. However, vaccines only work in individuals that are able to produce and maintain memory cells, which many older people are less able to do.

An important system that maintains cells, called autophagy, destroys and removes the ‘junk’ and toxic by products that all cells accumulate over time as a result of normal cell functions. Without autophagy, cells become less able to produce energy and they may die. Puleston et al. show that autophagy begins to fail in old mice, which prevents the formation of a proper memory response. In addition, mice that lack an important gene needed for autophagy are unable to produce memory cells after being infected with viruses such as influenza.

Puleston et al. found that boosting autophagy in older mice using a chemical called spermidine—which is also found naturally in many tissues—helped to restore the mice's ability to create and maintain memory cells. Spermidine-treated mice developed a stronger immunity to influenza after vaccination compared with other mice of a similar age. Further research is required to better understand how spermidine works to see if it could be developed into a drug that safely boosts the immune system of humans.

DOI:http://dx.doi.org/10.7554/eLife.03706.002

Prostaglandin D2 activates group 2 innate lymphoid cells through chemoattractant receptor-homologous molecule expressed on TH2 cells

Background

Activation of the group 2 innate lymphoid cell (ILC2) population leads to production of the classical type 2 cytokines, thus promoting type 2 immunity. Chemoattractant receptor-homologous molecule expressed on T_H2 cells (CRTH2), a receptor for prostaglandin D₂ (PGD₂), is expressed by human ILC2s. However, the function of CRTH2 in these cells is unclear.

Objectives

We sought to determine the role of PGD₂ and CRTH2 in human ILC2s and compare it with that of the established ILC2 activators IL-25 and IL-33.

Methods

The effects of PGD₂, IL-25, and IL-33 on the cell migration, cytokine production, gene regulation, and receptor expression of ILC2s were measured with chemotaxis, ELISA, Luminex, flow cytometry, quantitative RT-PCR, and QuantiGene assays. The effects of PGD₂ under physiologic conditions were evaluated by using the supernatant from activated mast cells.

Results

PGD₂ binding to CRTH2 induced ILC2 migration and production of type 2 cytokines and many other cytokines. ILC2 activation through CRTH2 also upregulated the expression of IL-33 and IL-25 receptor subunits (ST2 and IL-17RA). The effects of PGD₂ on ILC2s could be mimicked by the supernatant from activated human mast cells and inhibited by a CRTH2 antagonist.

Conclusions

PGD₂ is an important and potent activator of ILC2s through CRTH2 mediating strong proallergic inflammatory responses. Through IgE-mediated mast cell degranulation, these innate cells can also contribute to adaptive type 2 immunity; thus CRTH2 bridges the innate and adaptive pathways in human ILC2s.

The microRNA miR-182 is induced by IL-2 and promotes clonal expansion of activated helper T lymphocytes

After being activated by antigen, helper T lymphocytes switch from a resting state to clonal expansion. This switch requires inactivation of the transcription factor Foxo1, a suppressor of proliferation expressed in resting helper T lymphocytes. In the early antigen-dependent phase of expansion, Foxo1 is inactivated by antigen receptor-mediated post-translational modifications. Here we show that in the late phase of expansion, Foxo1 was no longer post-translationally regulated but was inhibited post-transcriptionally by the interleukin 2 (IL-2)-induced microRNA miR-182. Specific inhibition of miR-182 in helper T lymphocytes limited their population expansion in vitro and in vivo. Our results demonstrate a central role for miR-182 in the physiological regulation of IL-2-driven helper T cell-mediated immune responses and open new therapeutic possibilities.

Interferons direct Th2 cell reprogramming to generate a stable GATA-3(+)T-bet(+) cell subset with combined Th2 and Th1 cell functions

Current T cell differentiation models invoke separate T helper 2 (Th2) and Th1 cell lineages governed by the lineage-specifying transcription factors GATA-3 and T-bet. However, knowledge on the plasticity of Th2 cell lineage commitment is limited. Here we show that infection with Th1 cell-promoting lymphocytic choriomeningitis virus (LCMV) reprogrammed otherwise stably committed GATA-3(+) Th2 cells to adopt a GATA-3(+)T-bet(+) and interleukin-4(+)interferon-gamma(+) "Th2+1" phenotype that was maintained in vivo for months. Th2 cell reprogramming required T cell receptor stimulation, concerted type I and type II interferon and interleukin-12 signals, and T-bet. LCMV-triggered T-bet induction in adoptively transferred virus-specific Th2 cells was crucial to prevent viral persistence and fatal immunopathology. Thus, functional reprogramming of unfavorably differentiated Th2 cells may facilitate the establishment of protective immune responses. Stable coexpression of GATA-3 and T-bet provides a molecular concept for the long-term coexistence of Th2 and Th1 cell lineage characteristics in single memory T cells.

Blépharites du lupus érythémateux chronique

BACKGROUND

Discoid lupus erythematosus is a chronic skin disease frequently involving the face, scalp and ears. Palpebral lesions are rare. We report 4 cases of this uncommon localization. In one case, palpebral lesions were the sole manifestation of the discoid lupus erythematosus.

CASE REPORTS

Four patients aged between 26 and 45 Years had lesions of the lower eyelid as erythematous, infiltrated and scaly plaques. One patient, without diagnosis despite 2 skin biopsies of lesion, presented with a 2-Year history of blepharitis in the absence of any other cutaneous abnormality. In one case, chronic blepharitis has been present for 4 Years and associated with inflammatory arthralgia. Alopecia occurred 4 Years after the onset of blepharitis and led to the diagnosis of discoid lupus erythematosus. In 2 cases, blepharitis was associated with typical cutaneous lesions of discoid lupus erythematosus. Antimalaria drugs were very effective in 3 cases. In one patient the antimalaria drug failed, but thalidomide was effective.

DISCUSSION

The location of lesions on the eyelids in the absence of any other cutaneous abnormality is rare and can easily lead to the misdiagnosis of discoid lupus erythematosus. Most Authors mention a predilection of the lesions to the inferior portion of the eyelid, more specifically to the external third. The involvement of the eyelids with permanent scarring and severe eye impairment is explained by the long duration of the disease without diagnostic and appropriate treatment. Clinical examination is highly consistent with discoid lupus erythematosus: the lesions typically present as well-circumscribed, erythematous plaques with telangiectasia and scales and atrophy in long-standing disease. Antimalaria drugs are remarkably effective.

[Localized bullous pemphigoid induced by thermal burn]

BACKGROUND

Induced bullous pemphigoid is known to be triggered by drugs and some physical agents. Six cases of bullous pemphigoid induced by thermal burns have been reported since 1991.

CASE REPORT

We observed a bullous eruption around thermal burns of the left leg in a 89 year-old woman. Bullous pemphigoid was diagnosed by histological and immunohistochemical findings with a sub-epidermal blister and linear IgG and C3 deposition at the dermal-epidermal junction. Indirect immunofluorescence was negative. The eruption rapidly resolved with topical steroids.

DISCUSSION

We describe a bullous pemphigoid induced by a thermal burn. This case is original because the eruption was localized only around the site of the burn and healed with topical steroids. In the literature, there are 6 other cases reported but only one localized. We discuss the hypothesis of asymptomatic bullous pemphigoid exacerbated by presentation of bullous pemphigoid antigen by thermal burns or self immunization against antigens altered by burns.

Lipodystrophy associated with protease inhibitors

Lipodystrophies, characterized by reduction of subcutaneous fat over part or all of the body surface, are uncommon. Their causes are unknown. Recently, lipodystrophy has been reported in human immunodeficiency virus (HIV)-infected patients taking protease inhibitors, which have been recommended since 1996 as standard therapy for HIV disease in combination with nucleoside analogues. In these cases, lipodystrophy consists of an association of peripheral lipoatrophy with central adiposity. We report four HIV-infected men on protease inhibitors who developed a disfiguring lipodystrophy. In three of them, the protease inhibitor was administered for a mean duration of 21.5 months (range 19-23) with good immunological and virological responses. Patient 4 had been treated for 2 years with successive combinations of protease inhibitors with nucleoside analogues without success. The four patients progressively developed an increase in abdominal girth associated with fat wasting of the face and legs. Two of them had recurrent paronychia of the great toes. Triglyceride levels were moderately increased in all patients, and one had a slightly increased cholesterol level. One patient had elevated glucose and insulin plasma levels during a glucose tolerance test. In two patients, a deep biopsy taken from the thigh showed thinning of the subcutaneous fat without other morphological changes. Computed tomographic scans of the face and abdomen confirmed the loss of almost all subcutaneous fat of the cheek and temporal regions, and abdominal perivisceral fat accumulation. For patients 1-3, the protease inhibitor was replaced by a non-nucleoside reverse transcriptase inhibitor. Nine months later, dysmorphic changes had not regressed, but lipid abnormalities had returned to normal and the paronychia had disappeared.