Minimal change disease is defined by an abrupt onset of heavy proteinuria, low blood albumin, and elevated blood lipids. Under the electron microscope, the hallmark is the diffuse effacement of podocyte foot processes, the interdigitating projections that anchor these cells to the glomerular basement membrane and dynamically regulate filtration permeability. Yet light microscopy typically reveals an unremarkable glomerular architecture, and renal biopsies from many patients show no significant infiltration of T cells. This paradox has haunted nephrologists for decades: aberrant T cell activation is clearly implicated in driving podocyte injury, but the mechanism by which T cells are mobilized without ever visibly entering the kidney has remained elusive. Compounding the clinical problem, roughly twenty to thirty percent of adult patients develop steroid dependence or resistance, and some progress to end-stage renal disease.

The research team, led by investigators at Nanjing University Medical School and collaborating institutions, approached the problem by integrating clinical analysis with in vitro and in vivo experimental models. Their central hypothesis centered on extracellular vesicles—lipid bilayer-enclosed nanoscale particles that shuttle proteins, lipids, nucleic acids, and metabolites between cells. Exosomes, the smallest of these vesicles at thirty to one hundred fifty nanometers, have previously been found at elevated levels in the urine of patients with metabolic syndrome-associated kidney disease, renovascular hypertension, and preeclampsia, with their abundance correlating with proteinuria severity. What remained undefined was whether podocyte-derived exosomes could actually mediate communication between podocytes and T cells through antigen presentation.

In laboratory experiments, the researchers cultured mouse podocytes with a model antigen and interferon-gamma, an inflammatory cytokine. When naive T cells from OT-I transgenic mice—whose receptors specifically recognize the model antigen—were co-cultured with these activated podocytes, flow cytometry revealed a striking upregulation of the activation markers CD69 and CD25. Critically, adding GW4869, an inhibitor of exosome secretion, abolished this activation, indicating that the podocytes were stimulating T cells through released exosomes rather than direct contact. Characterization of the isolated vesicles confirmed their exosomal identity: they carried the canonical markers TSG101, ALIX, and CD63 but lacked the negative control protein calnexin, displayed a characteristic cup-shaped morphology under transmission electron microscopy, and measured fifty to one hundred fifty nanometers in diameter.

The mechanistic crux of the study lies in major histocompatibility complex class I molecules. Interferon-gamma stimulation significantly increased the expression of MHC-I, MHC-II, and the costimulatory molecules CD80 and CD86 on podocyte-derived exosomes. When the researchers generated podocytes deficient in MHC-I through lentiviral knockdown, exosomes from these cells completely failed to activate T cells. In vivo, the team depleted professional antigen-presenting cells by whole-body irradiation and then injected MHC-I-deficient exosomes alongside OT-I CD8-positive T cells into mice with puromycin aminonucleoside-induced minimal change disease. These mice exhibited significantly lower urinary protein-to-creatinine ratios and markedly fewer activated interferon-gamma-positive T cells in renal lymph nodes and spleen compared with controls receiving intact exosomes. The conclusion was unambiguous: CD8-positive T cell activation by podocyte exosomes is strictly dependent on MHC-I-mediated antigen presentation.

Perhaps the most elegant finding concerns the division of labor between podocyte exosomes and dendritic cells. While exosomes alone could trigger T cell activation, they could not drive T cell proliferation without dendritic cells present. In irradiated mice lacking dendritic cells, podocyte exosomes still activated kidney-resident memory T cells and worsened proteinuria, but systemic T cell expansion was blunted. When the researchers reconstituted dendritic cells by bone marrow-derived cell transfer, the full pathological cascade returned. This suggests a biphasic mechanism the authors describe as local activation followed by systemic amplification: exosomes mediate antigen presentation to tissue-resident memory T cells within the kidney to ignite early inflammation, while dendritic cells relay antigenic signals to secondary lymphoid organs, where they recruit and expand effector T cell populations. The data favor a reprocessing model in which dendritic cells internalize exosomes, degrade their cargo, and load peptides onto their own MHC-I molecules, rather than simply acquiring pre-formed complexes on their surface.

To establish clinical relevance, the team developed an autologous pairing system using samples from twenty patients with biopsy-confirmed minimal change disease and twenty with lupus nephritis. Plasma from each patient was split so that podocyte-derived exosomes, identified by the podocyte marker podocalyxin, could be isolated and paired with naive CD8-positive T cells from the same individual’s blood. Exosomes from both patient groups carried high levels of MHC-I, MHC-II, CD80, and CD86. Exposure to these autologous exosomes triggered robust T cell receptor signaling, evidenced by increased phosphorylation of ZAP-70 and Lck, followed by CD69 and CD25 upregulation, substantial proliferation by seventy-two hours, and elevated interferon-gamma secretion. Mass spectrometry of patient-derived exosomes identified 108 proteins unique to minimal change disease samples, including immunoglobulin variable region components and complement proteins, and bioinformatic screening against the Immune Epitope Database flagged twelve candidate autoantigens, with dermcidin prioritized on the basis of an HSP70-binding domain and an embedded HLA-A*03 epitope. Levels of exosomal MHC-I and CD80 correlated strongly with disease severity measures.

The therapeutic implications were tested through two complementary strategies. Pharmacological inhibition with GW4869 reduced renal exosome burden, lowered the urinary albumin-to-creatinine ratio, and decreased effector CD8-positive interferon-gamma-positive T cells in renal lymph nodes and spleen. More precisely, the team engineered podocyte-specific manipulation of Rab27a, a membrane-binding GTPase that governs the docking of multivesicular endosomes with the plasma membrane and thereby controls exosome release. Genetic overexpression of Rab27a in podocytes accelerated disease, while podocyte-specific knockout suppressed exosome secretion even more effectively than GW4869 and attenuated disease progression. Because GW4869 lacks tissue specificity and could disrupt beneficial exosome secretion in immune and endothelial cells, the podocyte-restricted genetic approach provides a cleaner proof of principle, pointing toward kidney-targeted nanocarrier delivery systems or CRISPR-based spatiotemporal control of Rab27a as future therapeutic avenues.

The study’s authors acknowledge that the candidate autoantigens remain at the level of computational prediction and will require direct validation through MHC-I immunopeptidomics and autologous T cell priming assays. Mouse models also cannot fully recapitulate human disease, and questions remain about whether exosomes influence B cells and macrophages as well. Nevertheless, the work fundamentally redefines podocytes as non-classical antigen-presenting cells and identifies a concrete, targetable pathway—Rab27a-dependent exosome release—linking podocyte injury to systemic T cell immunity. For a disease in which twenty to thirty percent of adult patients fail first-line steroid therapy, the prospect of intercepting these molecular messengers before they mobilize the immune system represents a compelling new frontier in precision nephrology.

Subject of Research: Podocyte-derived exosome-mediated antigen presentation and CD8-positive T cell activation in minimal change disease

Article Title: Podocyte-derived exosomes instruct dendritic cell-dependent CD8 + T cell activation and proliferation in renal inflammation

Article References: Qian, B., Mao, S., Chen, Y., Liu, Y., Zhang, M., Zhu, D., Zen, K., Wang, Y., Liu, Z., & Li, L. (2026). Podocyte-derived exosomes instruct dendritic cell-dependent CD8+ T cell activation and proliferation in renal inflammation. Journal of Advanced Research, 88, 885-898. https://doi.org/10.1016/j.jare.2026.01.032

Image Credits: AI Generated

DOI: 10.1016/j.jare.2026.01.032

Keywords: podocytes, exosomes, minimal change disease, CD8 T cells, MHC-I, dendritic cells, Rab27a, nephrotic syndrome, antigen presentation, renal inflammation, extracellular vesicles, proteinuria

The story begins when a previously healthy five-year-old girl was referred to the neurology unit with a fixed right mydriasis, a persistently dilated pupil, and complete retinal detachment in the same eye. Notably, she had never experienced fever or eye pain, features that might otherwise have steered clinicians toward an infectious or inflammatory process of a different character. Brain magnetic resonance imaging revealed severe right optic neuritis, appearing as hyperintensity on T2-weighted sequences, and serum testing detected anti-MOG antibodies at a low titer of 1:10. On the strength of these findings, the team diagnosed MOGAD, an autoimmune condition in which antibodies target myelin oligodendrocyte glycoprotein, a protein on the surface of myelin sheaths in the central nervous system, and initiated monthly intravenous immunoglobulin at a dose of 2 grams per kilogram.

The initial treatment did not hold the disease in check. Three months later, the girl suffered a brainstem relapse marked by vomiting, dysarthria, and ataxia. Repeat MRI showed contrast-enhancing lesions in both supra- and infratentorial regions, together with tonsillar herniation and obstructive hydrocephalus, a life-threatening buildup of cerebrospinal fluid pressure that required a third ventriculocisternostomy, a surgical bypass procedure. High-dose intravenous methylprednisolone pulses of 20 milligrams per kilogram per day were administered for seven days and produced only partial improvement. Despite ongoing therapy, a further relapse followed just three months later, this time presenting with cerebellar ataxia, dysarthria, and a right foot drop. The clinical picture was that of a refractory, relentlessly relapsing inflammatory disorder of the central nervous system, and the team escalated accordingly.

Faced with this refractory-relapsing MOGAD phenotype, the clinicians turned to rituximab, a monoclonal antibody that depletes CD20-positive B cells and is increasingly used as second-line therapy in antibody-mediated neuroinflammatory disease. The drug was given at 375 milligrams per square meter of body surface area weekly for four weeks, but it was discontinued after yet another relapse. Mycophenolate mofetil at 1000 milligrams per day was then added to the monthly immunoglobulin cycles, and this combination finally produced a more stable remission lasting three years. Even during this quiescent period, however, a subtle clue persisted: the girl’s anti-MOG antibody titers fluctuated, swinging between positive and negative results. The authors emphasize precisely this point in their critique, arguing that the role of MOG-IgG serum titer changes and oscillations should not be solely used to clarify the nature of neuroinflammatory pictures in children.

The remission shattered when the girl was 9.6 years old. She abruptly developed a crossed brainstem syndrome, a pattern of neurological deficits produced by a lesion interrupting nerve tracts and cranial nerve nuclei within the brainstem, manifesting as right lower limb hypertonia, flaccid paralysis of the left arm, anarthria, or complete loss of speech, lingual akinesia, and a fixed rightward deviation of the head. A new brain MRI revealed multiple hemorrhagic lesions lined through the thalamus, the nucleo-capsular regions, and the pons. Hemorrhagic transformation within inflammatory brain lesions of this severity is distinctly unusual for typical MOGAD and signaled that the underlying process was something far more destructive than a conventional demyelinating disease.

At this critical juncture, the clinicians returned to a physical sign that had been present all along: the girl’s silvery-gray hair and eyebrows. This peculiar pigmentation, easily overlooked or attributed to benign variation in a child with an autoimmune diagnosis, is in fact the hallmark of Griscelli syndrome, a group of autosomal recessive disorders defined by partial albinism. Acting on this reassessment, the team performed a molecular testing panel for hemophagocytic lymphohistiocytosis, or HLH, a hyperinflammatory syndrome in which immune cells attack the body’s own tissues and organs, using peripheral blood mononuclear cells. The panel revealed two variants in the RAB27A gene on chromosome 15q21: c.153+5G>A, a splice site variant that alters pre-mRNA splicing, and c.514_518del, a pathogenic five-base-pair deletion.

The molecular findings confirmed Griscelli syndrome type 2, catalogued as OMIM #607623, an ultrarare condition caused by mutations in RAB27A and characterized by partial albinism together with impaired cytotoxic activity of T cells and natural killer cells, carrying a risk of life-threatening hemophagocytic lymphohistiocytosis. The biology connects the two seemingly unrelated features of the case. The Rab27a protein is essential for the release of melanin from melanocytes into surrounding cells; when it is dysfunctional, melanin accumulates abnormally within melanocytes and is not transferred properly, producing the characteristic silvery-gray hair and skin hypopigmentation. The same protein is required for the release of cytolytic granules by cytotoxic lymphocytes, so its absence leaves the immune system unable to eliminate infected or activated cells, permitting uncontrolled immune activation that can culminate in the cytokine storm of HLH.

Importantly, the authors note that HLH may be virtually absent in some patients who present with a completely neurologic phenotype, even when molecular findings are fully consistent with Griscelli syndrome type 2. This phenotypic expansion, previously described in the literature in an eleven-year-old girl with Rab27A mutations and no hemophagocytosis, helps explain why the diagnosis remained hidden for more than five years in the present case. After the genetic confirmation, the girl was started on ruxolitinib, a Janus kinase inhibitor that dampens inflammatory signaling downstream of cytokine receptors, at a dose of 5 milligrams twice daily, and she was placed on the waiting list for hematopoietic stem cell transplantation, the only curative option for this disease. Sadly, a slowly progressive multiorgan failure developed five months later, and the girl died at the age of ten.

The case carries a pointed lesson for pediatric neurologists and immunologists alike. Rare genetic errors of immunity can coexist with hypopigmentation skin disorders, and the authors urge healthcare providers to recall that dysregulated immunity may be camouflaged by devastating neuroinflammatory pictures that begin with something as common as optic neuritis. Autoimmune test results, including anti-MOG positivity, may taint the true disease identity, because a positive MOG test does not automatically mean MOGAD. Low antibody titers, atypical clinical features such as absent pain, hemorrhagic lesions, relapses refractory to appropriately escalated immunotherapy, and fluctuating serology should all prompt a broader differential diagnosis that includes inborn errors of immunity. In such patients, recognizing subtle dysmorphic or pigmentation cues and pursuing molecular panels early can redirect treatment toward targeted immunomodulation and, ultimately, curative transplantation before irreversible damage accumulates.

Published as a letter in response to Aduru and colleagues’ finding that MOGAD is the most common cause of isolated optic neuritis in children, this report does not overturn that conclusion but complicates it. It stands as a reminder that the most frequent explanation is not always the correct one, and that in medicine, as in this child’s silver-gray hair, the most visible clue to a hidden diagnosis may be the one easiest to dismiss.

Subject of Research: Griscelli syndrome type 2 masquerading as MOG antibody-associated neuroinflammatory disease in a child

Article Title: A Lethal Progressive Neuroinflammation Disguised as MOGAD Revealing a Final Diagnosis of Griscelli Syndrome

Article References: Veredice, C., Arpaia, C., Contaldo, I., Capasso, A., & Rigante, D. (2026). A Lethal Progressive Neuroinflammation Disguised as MOGAD Revealing a Final Diagnosis of Griscelli Syndrome. Annals of Clinical and Translational Neurology, 13(8), 1740-1742. https://doi.org/10.1002/acn3.70470

Image Credits: AI Generated

DOI: 10.1002/acn3.70470

Keywords: Griscelli syndrome, MOGAD, optic neuritis, RAB27A, hemophagocytic lymphohistiocytosis, neuroinflammation, pediatric neurology, anti-MOG antibodies, partial albinism, rituximab, ruxolitinob, genetic diagnosis