Immunodeficiency Cases

Question 1

What are TRECs?

Answer 1

Pieces of DNA cut out during intrathymic T-cell receptor gene rearrangement

TRECs indicate that T cells are being made.

Question 2

What lab technique is used to count T cells?

Answer 2

Flow cytometry with fluorescent antibodies to CD3

Question 3

Naïve T cells will have __________.

Answer 3

CD4-RA (nAïve)

Question 4

To have SCID, you need to have defective ______________.

Answer 4

T cells (B cells may or may not be defective)

Note: this is why TRECs are used to screen for SCID, as opposed to KRECs.

Question 5

What protein is defective in X-linked SCID?

Answer 5

The common gamma chain

This is found in the IL-2 receptor, as well as in the receptors for interleukins 4, 7, and 9.

Question 6

What infections is a SCID baby likely to present with?

Answer 6

Opportunistic infections: PJP, Candida, Aspergillus, CMV, Enterovirus, and Mycobacteria

Question 7

What protein is responsible for cutting DNA in VDJ recombination?

Answer 7

RAG2

Question 8

Other than CD16, what surface receptor do NK cells have?

Answer 8

CD56

Question 9

True or false: NK cells are derived from myeloid precursors.

Answer 9

False. They are derived from lymphoid cells.

Question 10

Why was SCID added to the newborn screen?

Answer 10

Early diagnosis has been shown to save lives and money.

Question 11

What is required for a diagnosis of CVID?

Answer 11

1) At least one of the following: 
• Immune deficiency 
•Autoimmune manifestation
•Granulomatous disease
• Polyclonal proliferation 

2) Normal B and T cell count with low Ig.
3) Secondary causes – such as malignancy, drug toxicity, and protein loss –need to be excluded.
4) Diagnosis must occur after the fourth year of life.
5) Poor response to vaccines
6) No evidence of T cell dysfunction

Question 12

Memory B cells express which surface receptor?

Answer 12

CD27