Immunology: regulatory T cells: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · Immunology: regulatory T cells

Sample item

A 3-month-old boy has neonatal-onset type 1 diabetes, severe watery diarrhoea from autoimmune enteropathy and eczema. Which gene defect is most likely?

AFOXP3, causing absent regulatory T cellsBBTK, causing absent B cellsCAIRE, causing defective central toleranceDWAS, causing defective cytoskeletal function

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. FOXP3, causing absent regulatory T cells

IPEX syndrome is an X-linked disorder due to FOXP3 mutation, which is the master transcription factor of regulatory T cells. Loss of suppression causes multi-organ autoimmunity, including diabetes, enteropathy and eczema. Treatment is by immunosuppression and bone marrow transplantation.

Option by option

A. FOXP3, causing absent regulatory T cells (correct)
Correct. FOXP3 deficiency fits this triad of IPEX.
B. BTK, causing absent B cells
BTK defects cause agammaglobulinaemia with recurrent bacterial infections after 6 months.
C. AIRE, causing defective central tolerance
AIRE mutations cause APECED with candidiasis and endocrine failure that develops later in childhood.
D. WAS, causing defective cytoskeletal function
WAS mutations cause eczema, thrombocytopenia and infections without enteropathy and diabetes.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is A, FOXP3, causing absent regulatory T cells. IPEX syndrome is an X-linked disorder due to FOXP3 mutation, which is the master transcription factor of regulatory T cells.

Why is "BTK, causing absent B cells" not the answer?

BTK defects cause agammaglobulinaemia with recurrent bacterial infections after 6 months.

Why is "AIRE, causing defective central tolerance" not the answer?

AIRE mutations cause APECED with candidiasis and endocrine failure that develops later in childhood.

Why is "WAS, causing defective cytoskeletal function" not the answer?

WAS mutations cause eczema, thrombocytopenia and infections without enteropathy and diabetes.

What concept does this question test?

It tests Immunology: regulatory T cells in Microbiology. Loss of suppression causes multi-organ autoimmunity, including diabetes, enteropathy and eczema. Treatment is by immunosuppression and bone marrow transplantation.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Immunology: regulatory T cells?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.