Deficiency of Adaptive Immunity

Question 1

Describe SCID.

Answer 1

It is a single-gene disorder in which lymphoid cells development is impaired; can vary in severity; often X-linked

Question 2

What is the pathophysiology of Bruton’s?

Answer 2

Boys have defects in the gamma globulin gene, and are thus deficient in mature B cells.

Question 3

List the “CATCH-22” mnemonic for DiGeorge.

Answer 3

Calcium irregularities; appearance (fish-mouth); thymus; clefts (palate); heart (coarctation of the aorta); 22 chromosome

Question 4

Differentiate between primary and secondary immunodeficiency.

Answer 4

In primary immunodeficiencies, there are congenital defects in the bone marrow or thymus. In secondary immunodeficiency, the immune system is malfunctioning secondary to measles, AIDS, chemotherapy, or any other non-congenital source.

Question 5

What is the most common defect in X-linked SCID and autosomal SCID?

Answer 5

Defect in the IL-2 receptor, which is necessary for lymphoid development (X-linked) and lack of adenosine deaminase (autosomal recessive)

Question 6

Explain the pathophysiology and clinical signs of Bruton’s Agammaglobulinemia.

Answer 6

BA is an X-linked defect in the tyrosine kinase receptor; this receptor is necessary for B cell maturation, leading to lack of B cells and lack of antibody; chronic diarrhea, pneumonia; reason we don’t use OPV

Question 7

Why can some patients only manifest IgM?

Answer 7

Because they have defective CD40-ligand (CD154), which is the protein Tfh use to bind with B cells and induce isotype switching; this is called X-linked hyperIgM syndrome.

Question 8

What presentation is associated with CVID (common variable immunodeficiency)?

Answer 8

Milder symptoms, but still occasional recurring infections; can present in anyone up to age 50; low IgG

Question 9

B cell deficiencies are usually more _______, while T cell deficiencies are usually more _________.

Answer 9

extracellular (bacteria, parasites); intracellular (viruses, fungal)

Question 10

The most common immunodeficiency disorder is ______.

Answer 10

selective IgA syndrome, presenting with increased frequency of sinopulmonary infections and severe seasonal allergies

Question 11

What three viruses lead to secondary immunodeficiency?

Answer 11

Measles, mononucleosis, and cytomegalovirus

Question 12

What are the four ways immunodeficiency can be treated?

Answer 12

IVIG, thymus transplantation, prophylactic antibiotics, bone marrow transplant (SCID), and isolation (bubble boy)

Question 13

Why did bone marrow transplantation kill the bubble boy?

Answer 13

The bone marrow (from his sister) had latent cytomegalovirus and Ebstein-Barr virus–as most of us do–which killed him before the new immune system could take.