bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.64898/2026.03.02.708872

Evaluating 6- and 18-hour stimulation durations for natural killer cell degranulation (CD107a assay) to optimize workflow efficiency in a clinical immunology laboratory

Feehan, L.·Koutoufaris, L.·Dorsey, J.·Paessler, M.·Pandey, P.
View original source ↗Export metadata ↓

Abstract

BackgroundNatural killer (NK) cell degranulation is a key immune defense mechanism where exposure to tumor or virus-infected cells triggers the fusion of cytoplasmic granules containing apoptotic proteins, perforin, and granzyme with the cell membrane. This process transiently expresses CD107a on the NK cell surface, and measuring CD107a is a standard method to assess NK cell activity. MethodsWe compared two stimulation protocols differing only in duration (6-hour vs. 18-hour) using K562 target cells to induce NK cell degranulation. Isolated PBMCs without stimulation served as controls to assess spontaneous degranulation. Anti-CD107a-PE antibody was present throughout stimulation in both test and control samples. After stimulation, cells were stained with anti-CD45, anti-CD3, and anti-CD56 and analyzed by flow cytometry. ResultsFor 6 of 7 healthy controls, results from both methods fell within 2 standard deviations. Notably, longer (18-hour) stimulation resulted in lower CD107a expression than the 6-hour assay. Interlaboratory comparisons of two samples showed no significant difference (p>0.05). In a suspected hemophagocytic lymphohistiocytosis (HLH) case, two labs reported similarly reduced CD107a expression (9% and 7%). Inter-day variability was observed in a donor across both time points. The 6-hour assay showed higher sensitivity and specificity than the 18-hour assay. A resting period before ex vivo PBMC assays was found necessary. ConclusionStimulation periods beyond 6 hours are unsuitable for clinical NK degranulation assays. Screening for HLH should include multiple stimulants to improve assay reliability.

Explore related subjects

immunologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Feehan, L., Koutoufaris, L., Dorsey, J., Paessler, M., Pandey, P.. 2026-03-04. Evaluating 6- and 18-hour stimulation durations for natural killer cell degranulation (CD107a assay) to optimize workflow efficiency in a clinical immunology laboratory. https://doi.org/10.64898/2026.03.02.708872

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

TFAM Dependent Mitochondrial Fitness Limits CD8⁺ T Cell Immunopathology and Sustains Protective Immunity during Viral Pneumonia

During respiratory virus infection, CD8 T cells kill infected cells and establish antigen-specific memory, but mechanisms regulating these functions remain incompletely understood. Here, we identify mitochondrial transcription factor A (TFAM)-dependent mitochondrial fitness as a regulator of CD8 T cell function during influenza infection. Human CD8 T cells exhibited an age-associated decline in TFAM expression and mitochondrial function. To model this physiologically relevant decline and determine its consequences for antiviral immunity, we generated CD8 T cell-specific TFAM-haploinsufficient mice. TFAM insufficiency disrupted mitochondrial integrity and bioenergetics and increased mitochondrial DNA and oxidative stress. During influenza infection, TFAM-insufficient CD8 T cells exhibited increased cytotoxic and inflammatory activity associated with lung immunopathology without improved viral control. This early phenotype was followed by loss of effector function, diminished antigen-specific responses, reduced protection following adoptive transfer, and impaired heterosubtypic recall immunity. Thus, TFAM-dependent mitochondrial fitness is a cell-intrinsic regulator that limits immunopathology while sustaining recall immunity.

immunology↗
bioRxiv2026

Gasdermin E couples mitochondrial stress to STING-driven neuronal pyroptosis during Chandipura virus encephalitis

Neurotropic RNA viruses are major causes of fatal encephalitis worldwide, yet how infected neurons transition from antiviral defense to inflammatory cell death is not well characterized. Chandipura virus (CHPV), an emerging neurotropic rhabdovirus, causes acute, rapidly progressive encephalitis with high case fatality in children, but the mechanisms underlying its neuropathogenesis remain poorly defined. Here, we demonstrate that CHPV suppresses canonical RNA virus sensing early but subsequently switches to a mitochondria-driven innate immune program that culminates in inflammatory cell death. Early infection of neuronal cells with CHPV was marked by reduced levels of the mitochondrial antiviral adaptor protein, MAVS and attenuation of type I and III interferon responses. As infection progressed, mitochondrial dysfunction promoted accumulation of mtROS, mitochondrial accumulation of cleaved GSDME and cytosolic mtDNA release, triggering STING activation, which coincided with robust neuroinflammation and pyroptotic cell death. Pharmacological inhibition or genetic silencing of STING markedly attenuated inflammatory signaling, prevented pyroptotic membrane rupture and protected neurons from cell death without significantly affecting viral replication. In contrast, GSDME depletion reduced both viral replication and neuronal death. Notably, GSDME depletion markedly attenuated STING phosphorylation, while STING depletion also reduced GSDME activation, revealing functional coupling between these pathways during CHPV-induced neuronal injury. Collectively, our findings identify a mitochondria-GSDME-STING axis linking early immune evasion to neuroinflammation during CHPV infection, revealing a previously unrecognized mechanism of inflammatory neuronal death in viral encephalitis and highlighting STING as a potential therapeutic target in certain CNS viral infections.

immunology↗
bioRxiv2026

Mutanome-guided immunopeptidomics of blood plasma for neoepitope detection in solid tumors is constrained by cfDNA variant calling sensitivity and MS detection limits

Introduction: Neoepitopes form the basis of tumor-specific immune responses. Tissue biopsy, the primary source for neoepitope detection, is limited and invasive. Therefore, we aimed to identify neoepitopes by mutanome-guided immunopeptidomics from plasma of cancer patients. Methods: Mass spectrometry (MS) data analysis of HLA ligands from plasma (n = 4) was guided by patient-specific mutanomes of cell-free DNA (cfDNA) from plasma or tumor genomic DNA (tgDNA) from tissue. Matched tumor tissue and healthy donor plasma served as controls. Neoepitopes were validated with synthetic peptides, and immunogenicity was assessed using IFN-gamma ELISpot and intracellular cytokine staining. Results: Wild-type immunopeptidomes from tissue and plasma overlapped by 58%, with 91% of plasma HLA ligands rediscovered in tissue. 13 out of 15 tumor-associated HLA ligands detected in plasma were rediscovered in the matching tissue. However, no neoepitopes in plasma were identified by immunopeptidomics guided by cfDNA mutanomes, likely reflecting the limited overlap between cfDNA and tgDNA mutanomes (15%). Using the tgDNA mutanome as a complementary reference, two neoepitopes were detected in one patient's plasma, albeit at the MS detection limit. Both neoepitopes were also discovered in tissue, along with three tissue-exclusive neoepitopes. Two tissue-exclusive neoepitopes induced antigen-specific T cell responses in healthy donor PBMCs. Conclusion: In summary, plasma immunopeptidomics enables profiling of HLA ligands from wild-type proteins, including TAAs. In principle, neoepitope detection from plasma at the peptide level is feasible, but tissue remains the gold standard for variant calling and neoepitope identification. Improved detection methods may enable minimally invasive approaches in the future.

immunology↗