BACKGROUND. Idiopathic CD4 lymphopenia (ICL) is defined by persistent low CD4 counts (<300 cells/µL) in the absence of a causal infection or immune deficiency and can manifest with opportunistic infections. Approximately 30% of ICL patients develop autoimmune disease. The prevalence and breadth of their autoantibodies, however, and their potential contribution to pathogenesis of ICL remain unclear. METHODS. We hybridized 35 and 51 ICL patients’ sera to a 9,000 human proteome array and to a 128 known autoantigens array, respectively. Using a flow-based method, we characterized the presence of anti-lymphocyte Ab in the whole cohort of 72 patients, as well as the Ab functional capability of inducing antibody-dependent cell-mediated cytotoxicity (ADCC), complement deposition, and complement dependent cytotoxicity (CDC). We tested ex vivo the activation of the classical complement pathway on ICL CD4 T cells. RESULTS. All ICL patients had multitude of autoantibodies mostly directed against private (not shared) targets and unrelated quantitatively or qualitatively to the patients’ autoimmune disease status. The targets included lymphocyte intracellular and membrane antigens, confirmed by the detection by flow of IgM and IgG (mostly IgG1 and IgG4) anti-CD4 cell Ab in 50% of the patients with half of these cases triggering lysis of CD4 T cells. We also detected in vivo classical complement activation on CD4 T cells in 14% of the whole cohort. CONCLUSION. Our data demonstrate a high prevalence of autoantibodies in ICL, some of which are specific against CD4 T cells, may contribute to pathogenesis and may represent a potential novel therapeutic target.
Ainhoa Perez-Diez, Chun-Shu Wong, Xiangdong Liu, Harry A. Mystakelis, Jian song, Yong Lu, Virginia Sheikh, Jeffrey S. Bourgeois, Andrea Lisco, Elizabeth Laidlaw, Cornelia D. Cudrici, Chengsong Zhu, Quan-Zhen Li, Alexandra F. Freeman, Peter R. Williamson, Megan V. Anderson, Gregg Roby, John S. Tsang, Richard M. Siegel, Irini Sereti