Severe combined immunodeficiency

Severe combined immunodeficiency (SCID) is a group of inherited disorders marked by profound defects in T-cell development or function, often impairing B cells and natural killer cells as well.

T cell: A lymphocyte that coordinates immune responses or kills infected and abnormal cells. T-cell failure defines SCID and can also compromise B-cell antibody responses.
Newborn screening: Population testing of newborns for conditions that benefit from early identification and treatment. Screening for low T-cell receptor excision circles can identify SCID before infections begin.
X-linked severe combined immunodeficiency: A SCID subtype caused by pathogenic variants in IL2RG, usually affecting males. It is a common form, typically marked by absent T and natural killer cells with B cells present.
Combined immunodeficiency: An inherited immune disorder involving defects in both cellular and antibody-mediated immunity, with severity varying widely. SCID is the most profound end of the broader combined-immunodeficiency spectrum.
B cell: A lymphocyte that can produce antibodies and develop into memory cells. B-cell function may be absent or ineffective, even when B cells are present.
T-cell receptor excision circle: A circular DNA fragment produced during T-cell receptor gene rearrangement in developing T cells. Low levels in newborn blood spots signal markedly reduced production of new T cells.
ADA-SCID: A SCID subtype caused by inherited deficiency of adenosine deaminase. Its toxic metabolite buildup usually affects T cells, B cells, and natural killer cells.
DiGeorge syndrome: A congenital disorder commonly caused by a 22q11.2 deletion, which can impair thymic development and T-cell production. It can cause T-cell deficiency, but its developmental cause and accompanying features differ from SCID.
Natural killer cell: An innate lymphocyte that kills infected or cancerous cells without antigen-specific receptors. Some SCID mutations disrupt natural killer cell development alongside T cells.
Hematopoietic stem cell transplantation: Treatment that replaces or restores blood-forming stem cells to reconstitute blood and immune systems. It can establish durable immune function by providing healthy immune-cell precursors.

Linked from 12 pages