What type of immunodeficiency is typically characterized by normal T cell activity paired with absent or reduced antibody responses?

The type of immunodeficiency characterized by normal T cell activity while having absent or reduced antibody responses is known as Common Variable Immunodeficiency (CVID). In CVID, individuals have a defect in the B cells that prevents them from producing adequate immunoglobulins (antibodies), which leads to an increased susceptibility to infections. Despite the presence of normal or even sometimes elevated levels of T cell functioning, the impaired ability of B cells to mature into plasma cells and produce antibodies is what defines this disorder.

CVID is a diagnosis that often occurs later in life and can vary widely in its presentations, making it distinct from other immunodeficiencies like Hyper-IgM Syndrome, which specifically involves high levels of IgM but absent IgG, IgA, and IgE due to a different mechanism affecting T-B cell interactions. DiGeorge syndrome typically features a deficiency in T cell production due to thymic aplasia, and X-Linked Agammaglobulinemia is characterized by the absence of B cells leading to a complete lack of antibody production, rather than just reduced responses.

Thus, the characteristic of CVID—normal T cell activity paired with an inability to produce sufficient antibodies—effectively underscores its unique place within immunode