Rapid Whole Blood Flow Cytometric Test to Detect ICOS Deficiency in Patients with Common Variable Immunodeficiency

Abstract

Background/Aims: Common variable immunodeficiency (CVID) is the most common primary immunodeficiency. With respect to underlying defects it comprises a heterogeneous group of deficiencies. For some patients, distinct phenotypical abnormalities have been described, e.g. partial CD40L deficiency or complete ICOS deficiency. For the diagnosis of CD40L deficiency, a rapid whole blood flow cytometric method has been described several years ago. We aimed to determine if the same method can be used to diagnose ICOS deficiency. Methods: Whole blood from 8 healthy volunteers was stimulated for 4 and 20 h with phorbol 12-myristate 13-acetate (PMA) and ionomycin. Induction of ICOS expression was analyzed on CD8–CD3+ lymphocytes using three-color flow cytometry. Blood from a patient with diagnosed ICOS deficiency was also analyzed. Results: Whole-blood stimulation with PMA and ionomycin for 20 h resulted in a significant induction of ICOS expression on CD8–CD3+ lymphocytes in healthy volunteers. Four-hour incubation also demonstrated ICOS upregulation but to a much lower extent. In CD8–CD3+ lymphocytes from an ICOS-deficient patient, no ICOS expression could be induced following 20 h of stimulation. Conclusion: ICOS expression can be analyzed using a rapid whole blood flow cytometric test.