Flow Cytometry is a Reliable Tool in the Diagnosis of STK4 Deficiency

Abstract

Objective: STK4 (serine-threonine protein kinase 4) deficiency is categorized under combined immunodeficiencies, which are a subgroup of primary immunodeficiencies that profoundly affect T cells. Autosomal recessive STK4 deficiency is characterized by recurrent bacterial and viral infections, mucocutaneous candidiasis, and CD4 + T cell lymphopenia. Autoimmune comorbidities including hemolytic anemia and idiopathic thrombocytopenic purpura, and cardiac problems have been reported in STK4-deficient individuals. Current diagnostic tools for STK4 deficiency include next-generation sequencing (NGS) and Sanger sequencing that detect DNA sequence variations, and western blotting, which evaluates altered protein expression. However, all of these assays are timeconsuming; and in particular, NGS is a costly clinical use tool for a diagnostic laboratory. In comparison, flow cytometry is a rapid and reliable system commonly employed in the diagnosis of a wide range of primary immunodeficiency disorders. Materials and Methods: This study aimed to evaluate STK4 protein expression by flow cytometry among four patients with genetically confirmed STK4 gene mutations and seven healthy individuals. We calculated ΔMFI/cell values to investigate differences in protein expression among the subjects. Results: STK4 protein expression was reduced in the peripheral blood mononuclear cells obtained from all STK4-deficient patients compared to those from the healthy controls. Flow cytometry data was validated by western blotting. Conclusion: Flow cytometry is a rapid and reliable method to detect STK4 protein expression, qualified as a diagnostic tool to study STK4 deficiency.

The effect of mutatio-type on proteo-phenotype and clinico-phenotype in selected primary immunodeficiencies

“…If the variant is a reported causative variant for PIDs, genetic sequencing should be sufficient for the diagnosis. But, it should be considered that some genes responsible for PIDs are highly polymorphic such as ADA and TACI [17,18]. The effect of the variant of these polymorphic genes on the occurrence of the illness should be carefully examined.…”