Major Histocompatiblity Complex

Question 1

MHC

Answer 1

First recognized as the site of genes that cause T cells to reject tissues transplanted from unrelated donors to recipients
- MHC in humans is called Human leukocyte antigen complex

Question 2

Isotypes

Answer 2

Products of the different MHC 1 and 2 genes

Question 3

Alleles

Answer 3

Different forms of any given gene

Question 4

Allotypes

Answer 4

Different products of any given gene

Question 5

MHC diversity

Answer 5

Much smaller than that of TCR

• multiple gene families
• genetic polymorphism

Question 6

How many MHC class 1 isotypes do you have?

Answer 6

6 classes, get each one from your parent = 12 isotypes

Question 7

MHC class 1 locus

Answer 7

A-G

Question 8

Heterozygous

Answer 8

Individual that inherited 2 different forms (alleles) of the gene from parents
- better to be heterozygous than homozygous

Question 9

Homozygous

Answer 9

Individual that inherited the same forms (alleles) of the gene from parents

Question 10

HLA haplotype

Answer 10

Particular combination of HLA alleles found on a given chromosome 6

Question 11

HLA type

Answer 11

Combination of all HLA alleles a person has

Question 12

T cells can not recognize an _____ in the absence of _____

Answer 12

Antigen; MHC

Question 13

Difference between survivors and fatalities when an infectious disease strikes a population

Answer 13

The complement of MHC molecules present in each individual
- species wide MHC polymorphisms dramatically reduce likelihood that a single infectious agent will destroy an entire population

Question 14

Species most prone to genetic bottlenecking

Answer 14

• African cheetahs
• Florida panthers
• Lions in Tanzani

Question 15

Advantage of multiple MHC genes that arise from balancing selection

Answer 15

• contribute different peptide binding specificities
• greater number of pathogen derived peptides is presented during any infection
• strength of immune response against the pathogen is improved by increasing number of activated pathogen specific T cells
• high degree of MHC polymorphism ensures that most members of population are heterozygotes

Question 16

Directional selection

Answer 16

Favors certain MHC alleles at the expense of others and is imposed by specific, epidemic disease

• replaces older alleles with newer variants
• outcome is change, not balance

Question 17

MHC in domestic animals

Answer 17

• all mammals have MHC 1,2, and 3
• express differences in their conserved and variable regions
• MHC class 2 and 3 are orthologous
• MHC class 1 genes are paralogous
• overall molecular structure and function of MHC molecules does not differ significantly

Question 18

MHC class 3

Answer 18

• 4 genes for complement receptors, P450, TNF alpha, lymphotoxins, NK receptors, HSP

Question 19

Why do we have 2 different classes of MHC?

Answer 19

Helps to discriminate between different pathogens, do not need to send all pathogens thru the same pathway