To further support this, the frequency of Treg was inversely proportional to neopterin, a serum inflammatory protein.41 Several studies had since confirmed the reduction in peripheral blood Tregs (CD4+CD25+FOXP3+ or CD4+CD25+CD127−) with the greatest deficiencies identified in patients with autoimmune cytopenias or Freiburg Group 1a.42–45 Carter et al46 also suggested an association between decreased Tregs and CD8 T-cell exhaustion in CVID. This evidence concerns the gene FOXP3 and common variable immunodeficiency.