Objective: Lipopolysaccharide-responsive beige-like anchor (LRBA) plays a role in cell surface expression of inhibitory cytotoxic T lymphocyte-associated protein-4 (CTLA-4) protein. Recently identified LRBA deficiency leads to immune deficiency and autoimmunity and is diagnosed by mutation analyses and protein expression. Herein, we quantified stimulated and unstimulated intracellular LRBA protein expression by flow cytometry in LRBA deficiency patients.

Materials and Methods: Five LRBA deficient patients and seven healthy controls were evaluated. The LRBA expressions were assessed in peripheral-blood-mononuclear-cells in the presence or absence of phorbol-miristat-acetate and ionomycin stimulation. The difference in mean-fluorescence-intensity (ΔMFI) was calculated.

Results: The differences in mean-fluorescence-intensity values of LRBA by flow cytometry were 24±9 for the healthy controls and 4.8±2.8 for the patients. ΔMFIs were 20.8 for P3, 19 for P4 and 49.6 for healthy controls with stimulants and 4.8, 4.6 and 20.1 respectively without stimulants.

Conclusion: As a rapid and widely available assay, flow cytometric assessment of intracellular LRBA expression has been found to be an effective and reliable method in the identification of LRBA deficiency.