Major Histocompatibility Complex Flashcards

1
Q

What is the MHC?

A

The Major Histocompatibility Complex (MHC) is a set of closely linked genetic loci (genes of the MHC) that have been found to be overwhelmingly important in determining the fate of engrafted tissue. This set of linked loci is highly polymorphic and plays a central role in control of the cellular interactions responsible for physiological immune responsiveness.

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2
Q

What is the function of the MHC?

A

Their physiological function is to present peptides to T lymphocytes.

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3
Q

What are HLAs?

A

Human Leukocyte Antigens.

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4
Q

What are the Class I loci?

A

They include HLA A-C.

These molecules are present on virtually all nucleated cells and present antigen to CD8+ T lymphocytes.

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5
Q

What are the Class II loci?

A

It includes HLA D

These molecules are found on dendritic cells, B-lymphocytes, and macrophages and present antigen to CD4+ lymphocytes.

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6
Q

What are the Class III loci?

A

These are genes that happen to reside in the MHC region but do not present antigen to T lymphocytes.

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7
Q

What forms the platform for the bound protein on the MHCs?

A

Antiparallel beta pleated sheets

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8
Q

What do Class I MHCs bind?

A

Short peptides around 9 AAs in length

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9
Q

What do Class II MHCs bind?

A

Long polypeptides 13-17 AAs in length

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10
Q

What is the crucial part of the peptides that bind to the MHCs?

A

There are anchor proteins that are highly conserved and need a specific AA. (Ex: Tyrosine)

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11
Q

What is the expression of MHC receptors?

A

Codominant

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12
Q

Why is transplant of male organs into females usually avoided?

A

Males code for proteins that usually aren’t found in females.

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13
Q

What does T cell response to antigen depend on?

A

A specific T cell response to antigen (Ag) on cell surfaces depends not on recognition of the Ag alone but on recognition of an antigenic peptide in the groove of an MHC molecule on the cell surface.

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14
Q

What is MHC restriction?

A

The dependence of the T cells specific reactivity on foreign Ag plus MHC products rather than on foreign Ag alone is called
MHC Restriction.

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15
Q

What do CD4 and CD8 bind?

A

CD4 and CD8 bind non-polymorphic regions of the MHC receptor

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16
Q

What is the structure of the Class I MHC receptor?

A

α2 - α1

α3 - β2

17
Q

What is the structure of the Class II MHC receptor?

A

β1 - α1

β2 - α2

18
Q

Are Class I and II α and β chains encoded by the same genes?

A

No. MHC class I a chains and MHC class II a chain and ß chains are encoded by separate genes of the MHC locus.

19
Q

How many Class I and Class II MHCs are expressed in individuals?

A

Each individual expresses 3 maternal and 3 paternal class I molecular types, as well as 3 maternal and 3 paternal class II molecular types.

20
Q

Does recognition occur when the antigen matches and the MHC matches?

A

Yes

21
Q

Does recognition occur when the antigen does not match and the MHC matches?

A

No

22
Q

Does recognition occur when the antigen matches and the MHC does not match?

A

No