*Article* **Patients with Common Variable Immunodeficiency Complicated by Autoimmune Phenomena Have Lymphopenia and Reduced Treg, Th17, and NK Cells**

**Ewa Wi ˛esik-Szewczyk 1,\*, Elzbieta Rutkowska ˙ 2, Iwona Kwiecie ´n 2, Marcelina Korzeniowska 1, Dariusz Sołdacki 1,3 and Karina Jahnz-Rózyk ˙ <sup>1</sup>**


**Abstract:** Most patients with primary immune deficiency suffer from recurrent infections; however, paradoxical autoimmune phenomena can also manifest. The aim of this study was to identify immunological markers of autoimmune phenomena associated with common variable immunodeficiency (CVID). The study included 33 adults with CVID divided into two groups: (1) those with noninfectious autoimmune complications (CVID-C (*n* = 24)) and (2) those with only infectious symptoms (CVID-OI (*n* = 9)). Flow cytometry of peripheral blood was performed and compared with systemic lupus erythematosus (SLE) patients (*n* = 17) and healthy controls (*n* = 20). We found that all lymphocytes were lower in CVID-C and SLE. NK cells were lowest in CVID-C. Th17 cells were significantly reduced in CVID-C and SLE. Tregs were significantly lower in CVID-C and SLE. Bregs did not significantly differ between any groups. Class-switched memory B cells were significantly lower in CVID-C and CVID-OI. Lastly, plasmablasts were significantly higher in SLE. Among the T cell subsets, CVID-C patients had lower naive and recent thymic emigrant CD4+ T cells. In conclusion, reduced Treg, Th17, and NK cells are features of CVID with autoimmune complications, and class-switched memory B cells can help distinguish patients with different causes of autoimmunity. Future studies are needed to confirm whether reductions of Treg, Th17, and NK cells might be a biomarker of more complicated CVID cases.

**Keywords:** B cell maturation; CD4+ cells; T cell maturation; primary immune deficiency; autoimmunity; connective tissue diseases
