Biology subjects

Alattar, H.

Publications and source records attributed to Alattar, H..

3 recordsLinked to original sources

bioRxiv2026

Glycosylated GM-CSF expands B-1b cells and B-1b plasma cells and programs them for immunosuppression

The myeloid growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF) exhibits paradoxical pro- and anti-inflammatory functions, but the factors determining these divergent outcomes remain unclear. Here, we report that this functional divergence is controlled by its glycosylation. Murine recombinant fully glycosylated GM-CSF (rgGM-CSF) specifically induces immunosuppressive cell types, whereas its recombinant non-glycosylated counterpart (rngGM-CSF) promotes effector immune cells. Using single-cell ATAC-sequencing and flow cytometry, we show that rgGM-CSF has a previously unrecognized ability to effectively expand IL-10+ LAG-3+ PD-L1+ B-1b plasma cells (PCs) with immunosuppressive properties and self reactive natural IgM secretion. Although rgGM-CSF also promotes the expansion of hematopoietic stem and progenitor cells (HSPCs) and monocytic myeloid-derived suppressor cells (M-MDSCs), adoptive transfer experiments demonstrate that the rgGM-CSF-induced B-1b PCs are responsible for an IL-10-dependent long-term protection in mice from experimental autoimmune-encephalomyelitis (EAE). Our data suggest that glycosylation enhances the systemic bioavailability and activity of GM-CSF and promotes the expansion of immunoregulatory cells rather than pro-inflammatory myeloid effector cells. Together, these results demonstrate that the dual activity of GM-CSF is controlled by its glycosylation, resulting in opposing immune functions. These findings support a re-evaluation of human rgGM-CSF (regramostim) as a potential therapeutic strategy for immunosuppression in transplantation and autoimmune diseases. Key pointsO_LIGlycosylated GM-CSF promotes B-1b cells and B-1b plasma cells expansion and establishes their long-term imprinting as IL-10+ LAG3+ PD-L1+ natural IgM secreting regulatory cells. C_LIO_LIAlbumin binding enhances the systemic activity of glycosylated GM-CSF in generating regulatory B-1b plasma cells. C_LIO_LIGlycosylated GM-CSF injections into mice expand M-MDSCs, but their suppressive iNOS production is only maintained short-term. C_LIO_LINon-glycosylated GM-CSF injections preferentially promote expansion of pro-inflammatory effector monocytes and neutrophils. C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=179 HEIGHT=200 SRC="FIGDIR/small/703206v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@1814c57org.highwire.dtl.DTLVardef@1bb0e95org.highwire.dtl.DTLVardef@1ba8011org.highwire.dtl.DTLVardef@12df69f_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

MDSC depletion during immunization with heat-killed Mycobacterium tuberculosis increases protection against BCG infection.

Tuberculosis (TB) is still one of the deadliest infectious diseases globally. Although i.d. BCG immunization offers limited protection, a vaccine based on Mycobacterium tuberculosis (Mtb) has yet to be approved. Our previous findings demonstrated that s.c. immunization with heat-killed Mtb significantly increased the number of monocytic myeloid-derived suppressor cells (M-MDSC) in mice. Therefore, we hypothesized that the defense against a subsequent BCG infection would be impaired in Mtb-immunized mice. Surprisingly, mice vaccinated with Mtb were protected against a BCG infection and showed elevated frequencies and activation of DC and mycobacteria-specific T cells despite high frequencies and suppressor activity of M-MDSC. Genetic ablation of CCR2+ monocytic cells or pharmacological intervention with all-trans retinoic acid (ATRA) reduced the frequency of Mtb-induced M-MDSC, enhanced frequencies, and activation of dendritic cells (DC) and CD4+ T cells, and resulted in decreased bacterial loads in the lung and spleen. These findings offer fresh perspectives on TB vaccination using heat-killed Mtb despite parallel unwanted vaccine-induced M-MDSC. M-MDSC depletion by ATRA further tips the balance towards immunity and should be considered an adjunct host-directed therapy with TB vaccines in humans.

immunology↗

bioRxiv2024

AMPK/ULK1 activation downregulates TXNIP, Rab5, and Rab7 and inhibits endocytosis-mediated entry of human pathogenic viruses

Cellular metabolism must adapt rapidly to environmental alterations and adjust nutrient uptake. Low glucose availability activates the AMP-dependent kinase (AMPK) pathway. We demonstrate that activation of AMPK or the downstream Unc-51-like autophagy-activating kinase (ULK1) inhibits receptor-mediated endocytosis. Beyond limiting dextran-uptake, this activation prevents endocytic uptake of human pathogenic enveloped and non-enveloped, positive and negative-stranded RNA viruses, such as yellow fever, dengue, tick-borne encephalitis, chikungunya, polio, rubella, rabies lyssavirus and SARS-CoV-2 not only in mammalian and insect cells but in precision-cut lung slices and neuronal organoids. However, receptor presentation at the cytoplasmic membrane was unaffected, indicating that receptor-binding remained unaltered and later steps of endocytosis were targeted. Indeed, AMPK pathway activation reduced early endocytic factors TXNIP, Rab5 and the late endosomal marker Rab7 amounts. Furthermore, AMPK activation impaired SARS-CoV-2 late-replication steps by reducing viral RNAs and proteins and the endo-lysosomal markers LAMP1 and GRP78, suggesting a reduction of early and late endosomes and lysosomes. Inhibition of the PI3K and mTORC2 pathways, which sense amino acids and growth factor availability, promotes AMPK activity and blocks viral entry. Our results indicate that AMPK and ULK1 emerge as restriction factors of cellular endocytosis, impeding the receptor-mediated endocytic entry of enveloped and non-enveloped RNA viruses.

microbiology↗