MHC

Question 1

MHC

Answer 1

MHC

• a complex genetic system composed of more than 200 genes, each of them having more than 100 allelles
• genes are on chromosome 6, on the short arm
• MHC genes code for cell surface proteins which control the adaptive immune response
• MHC genes are co-dominant and encode MHC-molecules

Question 2

the gene system is:

• poly….
• poly….

Answer 2

Polygenic: presence of multiple different genes with similar function

Polyallelic: presence of many alternative variants of a single gene

Question 3

How are MHC genes inherited? (2 key words plus explanation)

Answer 3

Codominant:
a form of dominance in which the alleles of a gene pair in a heterozygote are fully expressed thereby resulting in offspring with a phenotype that is neither dominant nor recessive

Polymorphism:
diversely varying from organism to organism within a species

Question 4

Localization of MHC I molecules

Answer 4

MHC class I
○ on surface of all nucleated somatic cells
○ most abundant on T-cells

Question 5

Localization of MHC II molecules

Answer 5

MHC class II
○ on immune cells:

§ B-Lymphocytes
§ antigen presenting cells
§ activated T-Ly, thymic epithelial cells

Question 6

MHC-restriction (def)

Answer 6

The ability of T-Lymphocytes to recognize Antigens bound to a definite class of self MHC molecules

• each TCR (T-cell receptor) recognizes a definite Antigen bound to a definite MHC - molecule

Question 7

general functions of MHC molecules

Answer 7

Function:
- present fragments of antigens to T cells (because the receptor of T cells can only recognize antigen fragments in complex with MHC proteins)

• help the recognition of self from nonself

Question 8

Functions of MHC class I molecules

Answer 8

• antigen presentation to T-cytotoxic cells
  MHC I - Tc - CD8
• viral and turmoral immunity (through Tc)
• are components of hormones and receptors (insulin, glucagone, EGFR)
• similar to genes for olphactorial receptors (receptors for smells) —– source of unique fragranes which affect recognition, sexual preferences etc.

Question 9

Functions of class II molecules

Answer 9

• antigen presentation to T-helpers
  MHC II - Th - CD4
• regulation of immune response
• pathogenesis of autoimmune disease
  (through antigenic mimicry (having similar antigens to host - not recognised by immune system); used by HIV and A. lumbricoides)

Question 10

Predisposition and resistance to disease trough certain MHC genes

Answer 10

• predisposition to disease: increased likelihood of developing a particular disease
  ○ f.ex. ankylosing spondylitis (disease where intervertebrate discs get ossified, type of athritis)
• resistance to disease:
  ○ B53 allel - HIV (allel presents virus effectively)
  ○ alleles also dermine which type of HIV an infected persons is (fast progressors or slow progressors)

Question 11

Structure of MHC class I

Answer 11

• are transmembrane glycoproteins
• 1 alpha - polypeptide chain (with 3 alpha - domains)
• invariable 1 beta - microglobulin (CD8 of Tc binds to invariable domain)

Question 12

Structure of MHC class II

Answer 12

• are transmembrane glycoproteins
• variable 1 alpha polypeptide chain
• variable 1 beta polypeptide chain