Comparative analysis of protein expression profiles with genotypes in the diagnosis of Inborn Errors of Immunity.

Background: Inborn Errors of Immunity (IEIs) are genetic diseases resulting from harmful genetic variations that hinder the proper functioning of the immune system. The broad range of IEIs involves multiple systems, presenting characteristics similar to allergies, autoimmune or inflammatory diseases, and malignancies. Given this complexity, there is an urgent need for a precise multi-parametric molecular diagnostic approach.

Objective: In this work, we demonstrated the effectiveness of accurate diagnosis by flow cytometry in patients with IEI by comparing genotype analysis with the expression levels of particular proteins and signaling activities.

Methods: We examined the expression levels or signaling activities of 28 cell surface and intracellular proteins using flow cytometry in a cohort of 352 patients and 189 healthy controls, in conjunction with genotype analysis for comparison. Results: We identified alterations in protein expression in 60 individuals, among them, 55 exhibited the presence of an underlying pathogenic mutation. Complete loss of protein expression was observed in seven patients, constituting 2% of the total, while reduced protein expression was noted in 35 patients (9%). Notably, despite mutations in the relevant genes, protein expression levels were normal in five patients (2%), in all investigated patients. 37% of patients had elevated signaling activity, and 17% were suggestive of a particular IEI diagnosis following protein expression analysis.

Conclusion: The correspondence between flow cytometry-based protein analyses and genotype facilitates a prompt diagnosis, providing patients with swift access to therapeutic options.