Primary T Cell Immunodeficiencies and Autoimmunity

Abstract SCI-21

There are a variety of primary T cell immunodeficiencies that can impair T cell differentiation or T cell activation. The latter include CD38δ deficiency, ZAP70 deficiency, Ca⁺⁺ influx deficiency (ORAI1 and Stim1 deficiencies), and ITK deficiency as well. A new T cell activation deficiency as observed in a patient with defective T cell receptor triggered T cell activation and low CD4 T cell counts will be reported. A remarkable and quasi constant feature shared by all those T cell activation defects is the occurrence of autoimmune diseases, mostly related to autoantibodies, and inflammation such as colitis or panniculitis. Several mechanisms can account for these findings that include defective regulatory T cell development or function, defective negative selection impaired intrinsic feedback mechanism as well as non TCR-mediated T cell activation ultimately leading to proinflammatory cytokines release and autoantibody production by B cells. Another new form of primary T cell immunodeficiency with autosomal recessive inheritance observed in four patients from two families will be described. It is characterized by defective survival of naïve T cells. There again, autoimmunity appeared to be a significant component of the phenotype. Collectively, these results indicate that further insight into the role of key molecules in T cell activation/survival is provided by the analysis of new primary immunodeficiency phenotypes. In addition, the occurrence of autoimmunity in these settings stresses on one hand the role of T cells in the control of reactivity to self and, on the other hand, should be considered in the therapeutic strategy of these conditions.