Common combined B-cell and T-cell disorders

Question 1

What are common combined B-cell and T-cell disorders?

Answer 1

• SCID
• Ataxia-telangiectasia
• Hyper IgM Syndrome
• Wiskott-Aldrich

Question 2

What is Severe combined immunodeficency (SCID)?

Answer 2

There is a B-cell + T-cel def due to:
1) defective IL-2 receptor

2) Adenosine deaminase deficiency
Presents with failure to thrive, diarrhea, thrush; recurrent viral, bacterial, fungal and protozoal infections

3) Absent B-cells and T-cells so absent germinal centers and thymic shadow
4) Tx: bone marrow transplant

Question 3

What is Ataxia-telangiectasia?

Answer 3

it is a defect in ATM gene; defect in detection of DNA damage, so mutations accumulate during replication; lymphopenia.

Triad of sx (3 A’s):

1) Ataxia (cerebellum defects)
2) spider Angiomata (telangiectasia)
3) IgA deficiency (and IgG and IgE def.)
4) AFP increased

Question 4

What is Hyper IgM Syndrome?

Answer 4

It is a defect in CD40L on Th cells🡪results in defective class-switching of B-cells (which have CD40 (receptor))
—Primarily T-cell independent activation of B-cells occurs, so only IgM produced

Question 5

What is Wiscott-Aldrich?

Answer 5

It is a mutation in the Wiskott-Aldrich (WAS) gene, leukocytes and platelets not able to structure actin in cytoskeleton🡪defective leukocytes and platelets; Defective antigen presentation by leukocytes; sx: “water”

• –Wiskott-Aldrich
• –Thrombocytopenia
• –Eczema
• –Recurrent infections