GATE 2023 BT – Question 17

General Biology · Immunology: MHC, antigen processing and presentation, regulation, tolerance, hypersensitivity, autoimmunity, immunodeficiency, graft vs host disease, vaccines · 1 mark · Multiple choice

Dendritic cells are involved in cross-presentation of antigens. Which of the following protein(s) is(are) required for cross-presentation? P. Basic leucine zipper ATF-like transcription factor 3 (BATF3) Q. Membrane associated ring-CH-type finger 1 (MARCH-1) R. Solute carrier family 10 member 1 (SLC10A1) S. Class II-associated invariant chain peptide (CLIP)

P only
P and R only
P, Q and R only
S only

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Correct answer: (A) P only

Explanation

**Cross-presentation** lets dendritic cells present exogenous antigen on **MHC class I**, to activate CD8⁺ T cells.

**P. BATF3:** this transcription factor is required for the development of the cDC1 (CD8α⁺/CD103⁺) dendritic cells that are specialised for cross-presentation. Batf3-deficient mice lack these cells. ✓
**Q. MARCH-1:** an E3 ligase that ubiquitinates MHC class II and CD86 and so controls MHC-II surface levels. It is not needed for cross-presentation. ✗
**R. SLC10A1:** a sodium-taurocholate (bile acid) transporter in hepatocytes. Unrelated. ✗
**S. CLIP:** the invariant-chain fragment that occupies the MHC-II groove until it is exchanged. It belongs to the MHC-II pathway. ✗

Answer **P only** (A).