Antigen Presentation and MHC Molecules

Question 1

the major histocompatibility complex is also called what in humans?

Answer 1

human leukocyte antigen complex (HLA)

Question 2

how are MHC class I and class II molecules the same?

Answer 2

• act as a cell-surface vessel for holding or displaying fragments of antigens
• T-alpha-beta engage with class I and II via their T cell receptors on the cell surface

Question 3

How are MHC class III molecules different from class I and II?

Answer 3

• region encodes complement proteins and tumor necrosis factor
• functions are unrelated to antigen presentation

Question 4

what is a HAPLOtype?

Answer 4

all the alleles encoded by the genes in the complex are inherited in a set one from mother and one from father (co-dominantly expressed)

Question 5

why are the MHC haplotypes used for paternity and signature/fingerprint testing?

Answer 5

they are highly polymorphic within the human race meaning each of the molecules is very different between persons

Question 6

how many different classes of class I and class II molecules are there in a person?

Answer 6

6 different class I
12 different class II

Question 7

what is the structure of the MHC Class I molecule?

Answer 7

• a peptide with 3 domains ( a1, a2 and a3), a transmembrane C terminal and a beta-2 microglobulin

Question 8

what does the a1 and a2 domains of a MHC class I molecule form? what does it carry?

Answer 8

forms a cleft that carries antigenic peptides of 8-10 amino acids one at a time that are very polymorphic

Question 9

do MHC molecules have broad specificity?

Answer 9

yes, many different peptides can fit the same MHC molecule

Question 10

what binds to the a3 domain of MHC class I molecules?

Answer 10

CD8 molecules on T cells

Question 11

are the amino acids in the a3 domain of class I MHC molecules polymorphic?

Answer 11

no

Question 12

what does it mean that the MHC class I molecules are the classical transplant antigens?

Answer 12

MHC class I molecules are encoded by the highly polymorphic HLA genes, specifically HLA-A, HLA-B, and HLA-C and these molecules are the primary targets of the immune system during organ transplant rejection.

Question 13

which class of MHC molecules are used for paternity testing?

Answer 13

class I

Question 14

which class of MHC molecules present endogenous antigens to CD-8 cytotoxic T-cells?

Answer 14

class I

Question 15

what is the structure of the MHC Class II molecule?

Answer 15

• an alpha peptide with two domains (a1 and a2) and a transmembrane C terminal
• a beta peptide with two domains (b1 and b2) and a transmembrane C terminal

Question 16

what does the a1 and b1 domains of a MHC class II molecule form? what does it carry?

Answer 16

forms a cleft that carries antigenic peptides of 10-20 amino acids one at a time that are very polymorphic

Question 17

what binds to the b2 domain of MHC class II molecules?

Answer 17

CD4

Question 18

are the amino acids in the a1 and b1 domain of class II MHC molecules polymorphic?

Answer 18

yes

Question 19

are the amino acids in the a2 and b2 domain of class II MHC molecules polymorphic?

Answer 19

no

Question 20

where are MHC class II found and what do they present?

Answer 20

found on antigen presenting cells and present antigens to CD4 helper T cells

Question 21

what are professional antigen presenting cells (APC)?

Answer 21

cells that constitutively express MHC class II molecules

Question 22

what are the types of professional APC?

Answer 22

• macrophage and macrophage like cells (langerhans and dendritic cells)
• B lymphocytes

Question 23

what are occasional presenter cells?

Answer 23

cells that express MHC class II molecules when induced

Question 24

what are examples of occasional presenters?

Answer 24

• cytokines
• karatinocytes
• endothelial cells
• epithelial cells

Question 25

what MHC class molecules present exogenous antigens and which one presents endogenous antigens?

Answer 25

• class I presents endogenous
• class II present exogenous

Question 26

which class of MHC molecules present exogenous antigens to CD-4 T helper cells?

Answer 26

class II

Question 27

CD-1 shares structural similarities to what MHC class molecule but functionally overlaps with ?

Answer 27

class I
class II

Question 28

CD-1 molecules present what type of antigens to what cells?

Answer 28

lipid-containing antigens to NKT cells and T-gamma-delta