We have shown that nanoparticles (NPs) can be used as ligand-multimerization platforms to activate specific cellular receptors in vivo. Nanoparticles coated with autoimmune disease-relevant peptide-major histocompatibility complexes (pMHC) blunted autoimmune responses by triggering the differentiation and expansion of antigen-specific regulatory T cells in vivo. Here, we define the engineering principles impacting biological activity, detail a synthesis process yielding safe and stable compounds, and visualize how these nanomedicines interact with cognate T cells. We find that the triggering properties of pMHC-NPs are a function of pMHC intermolecular distance and involve the sustained assembly of large antigen receptor microclusters on murine and human cognate T cells. These compounds show no off-target toxicity in zebrafish embryos, do not cause haematological, biochemical or histological abnormalities, and are rapidly captured by phagocytes or processed by the hepatobiliary system. This work lays the groundwork for the design of ligand-based NP formulations to re-program in vivo cellular responses using nanotechnology.

Germinal center follicular T helper (GCTfh) cells are essential players in the differentiation of B cells. Circulating follicular T helper (cTfh) cells share phenotypic and functional properties with GCTfh cells. Distinct subpopulations of cTfh with different helper capabilities toward B cells can be identified: cTfh1 (CXCR3+CCR6−), cTfh2 (CXCR3−CCR6−), and cTfh17 (CXCR3−CCR6+). Alterations in cTfh function and/or distribution have been associated with autoimmunity, infectious diseases, and more recently, with several monogenic immunodeficiencies. Common variable immunodeficiency (CVID) disease is the commonest symptomatic primary immunodeficiency with a genetic cause identified in only 2–10% of patients. Although a heterogeneous disease, most patients show a characteristic defective B cell differentiation into memory B cells or antibody-secreting cells. We investigated if alterations in CVID cTfh cells frequency or distribution into cTfh1, cTfh2, and cTfh17 subpopulations and regulatory follicular T (Tfr) cells could be related to defects in CVID B cells. We found increased percentages of cTfh exhibiting higher programmed death-1 expression and altered subpopulations distribution in smB− CVID patients. In contrast to smB+ patients and controls, cTfh from smB− CVID patients show increased cTfh1 and decreased cTfh17 subpopulation percentages and increased CXCR3+CCR6+ cTfh, a population analogous to the recently described pathogenic Th17.1. Moreover, Tfr cells are remarkably decreased only in smB− CVID patients. In conclusion, increased cTfh17.1 and cTfh1/cTfh17 ratio in CVID patients could influence B cell fate in smB− CVID patients, with a more compromised B cell compartment, and the decrease in Tfr cells may lead to high risk of autoimmune conditions in CVID patients.

Background: Toxic epidermal necrolysis (TEN) is a rare severe acute exfoliative drug-induced skin disorder which has recently been ascribed to alterations in the control of keratinocyte apoptosis, mediated by an interaction between the cell surface death receptor Fas and its respective ligand. A therapeutic approach with intravenous immunoglobulins (IVIG) associated with pulse methylprednisolone, based on the inhibition of Fas-mediated keratinocyte death by naturally occurring Fas-blocking antibodies included in human immunoglobulin preparations, has produced good preliminary results. Objective: To analyse the efficacy of IVIG in the treatment of TEN. Patients: Nine patients with erythematous body surface area ranging from 38 to 85% and dermo-epidermal detachment from 4 to 37% were treated. Results: Eight patients were healed and 1 died of septic shock and multiple organ failure. Interruption of further epidermal detachment occurred after an average of 4.8 days from the onset of IVIG therapy. Complete wound healing occurred after an average of 12 days. Concerning complications, 3 out of 8 surviving patients had acute respiratory failure requiring mechanical ventilation and 1 acute renal failure was treated with dialysis. Late sequelae were limited to dyschromia and nail dystrophies. No hypertrophic scars were observed. Conclusion: IVIG therapy represents a safe and valid approach for TEN.

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