The key proteins involved in functioning of Treg, including FoxP3, Granzyme A, XCL1 (lymphotactin), pSTAT5 (phosphorylated signal transducer and activation of transcription-5 protein), and GITR (glucocorticoid induced tumor necrosis factor receptor related protein) were found to be significantly reduced in patients with CVID with autoimmunity. This evidence concerns the gene FOXP3 and common variable immunodeficiency.