Question

answer all the questions answering one question is not helpful

1. A helper T cell is capable of helping another cell because it expresses a protein on its surface that binds to a different protein on the surface of the cell being helped. What are these proteins (on the T cell, and on the cell being helped)?

	CD28, and B7
	TNF, and TNFR

	Class I MHC, and TCR
	CD40L, and CD40

CTLA-4, and B7

2. Helper T cells are restricted to recognizing antigen in the context of MHC class __ because they express CD__.

	MHC class I, CD4
	MHC class II, CD4

	MHC class I, CD8
	MHC class II, CD8

None of the above are correct

3. Dendritic cells at epithelial barriers can be activated after an invasion by pathogen, and then the function and behavior of DCs changes. In what way?

	Upregulated expression of MHC proteins
	Upregulated expression of costimulatory molecules

	Migration to a draining lymph node or other secondary lymphoid tissue
	All of the above are correct

None of the above are correct

4. Why do MHC class II complexes fail to load with antigenic peptides in the endoplasmic reticulum?

	Because MHC class II proteins aren't made in the ER.
	Because binding of TCR prevents this.

	Because the Ii protein blocks the antigen-binding site.
	Because the TAP transporter doesn't function in cells that express MHC class II.

All of the above are correct.

Answer 1

(1) The answer to question 1 is option (a) CD28 and B7

- Explanation:- on the T-cell the protien is CD28 receptors and on the cell being helped , the protien is B7 protiens which constitute CD80 and CD86.

(2).Helper T-cell are restricted to recognising antigen in context of MHC class II because they express CD4.

So the answer is option (b) MHC class-II , CD4

3. the answer to the question will be option (d) all of the above are correct.

Explanation.:-

- upregulated expression of MHC protiens.

- upregulated expression of costimulatory molecules like B7 Protiens.

- migration to a draining lymph node.

(4) the answer to this question is option (c) Because the li protiens block the antigen-binding site.

Explanation:- the MHC class II protien in the rough ER , has its antigen binding site being blocked by the invariant chain called the li protiens. The li protiens prevent the MHC molecule from binding to antigenic peptides.

Hopefully it helps thanks.