Defects in T cells - part of severe combined immunodeficiencies (SCID)

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago

Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

Severe combined immunodeficiencies (SCIDs) represent a heterogeneous group of disorders. The most common SCID is X-linked and, therefore, most cases are diagnosed in male infants.

Defects in T cells

- CD8 lymphopenia can be caused by BLS1 (MHC1 deficiency) and ZAP70 deficiency

- CD4 lymphopenia can be caused by BLS2 (MHCII deficiency), p56lck deficiency,

and HIV infection
- see more examples in the figure below

When diagnosing SCID, focus on B and NK phenotype because T cells are aslmost always absent/deficient with few exceptions.

Severe combined immunodeficiency (SCID) - 4 groups according to T/B/NK cells (click to enlarge the image).

Receptors for each of the following cytokines share the common gamma chain except which one?

A. IL-2

B. IL-7

C. IL-9

D. IL-15

E. IL-5

Answer: E.

Lack of a signal through which cytokine receptor accounts for the lack of T cell maturation in X-linked SCID?

A. IL-2

B. IL-7

C. IL-9

D. IL-15

E. IL-5

Answer: B.

Lack of a signal through which cytokine receptor accounts for the lack of NK cell maturation in X-linked SCID?

A. IL-2

B. IL-7

C. IL-9

D. IL-15

E. IL-5

Answer: D.

References

Practice parameter for the diagnosis and management of primary immunodeficiency. Ann Allergy Asthma Immunol 2005 May;94(5 Suppl 1):S1-63.

Algorithm 1: General Approach for the Diagnosis of Primary Immunodeficiency

Algorithm 2: Diagnosis of Humoral Immunodeficiency

Algorithm 3: Diagnosis of Cellular and Combined Immunodeficiencies

Algorithm 4: Diagnosis of Phagocyte Defects

Algorithm 5: Diagnosis of Complement Deficiency

Algorithm 6: General Considerations for Therapy of Primary Immunodeficiency

Published: 09/10/2010
Updated: 09/12/2010