In what condition do you observe elevated levels of double negative αβ T cells?

Elevated levels of double negative αβ T cells are particularly associated with Autoimmune Lymphoproliferative Syndrome (ALPS). This condition arises from defects in the Fas or Fas ligand, which are crucial for apoptosis of lymphocytes. In ALPS, the inability to effectively induce apoptosis leads to an accumulation of lymphocytes, including double negative T cells (which lack both CD4 and CD8 markers). These double negative T cells have been noted to be a hallmark of ALPS and may contribute to the excessive immune activation and autoimmune features seen in this syndrome.

In contrast, the other conditions mentioned do not typically exhibit elevated levels of double negative αβ T cells due to their different underlying mechanisms. Common Variable Immunodeficiency (CVID) involves impaired antibody production but is not characterized by the proliferation of these specific T cells. Severe Combined Immunodeficiency (SCID) indicates a complete or near-complete absence of T and B lymphocytes, making the presence of double negative T cells unlikely. X-linked Agammaglobulinemia, like SCID, is marked by a significant reduction in B cells and also does not present with elevated double negative T cells.

Thus, the presence of elevated double negative αβ T cells is a