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Flashcards in MHC Deck (12):
1

MHC

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

2

the gene system is:
- poly....
- poly....




Polygenic: presence of multiple different genes with similar function

Polyallelic: presence of many alternative variants of a single gene


3

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


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

4

Localization of MHC I molecules

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

5

Localization of MHC II molecules

MHC class II
○ on immune cells:

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

6

MHC-restriction (def)

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

7

general functions of MHC molecules

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

8

Functions of MHC class I molecules

- 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.


9

Functions of class II molecules

- 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)

10

Predisposition and resistance to disease trough certain MHC genes

- 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)

11

Structure of MHC class I

- are transmembrane glycoproteins

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

12

Structure of MHC class II

- are transmembrane glycoproteins

- variable 1 alpha polypeptide chain
- variable 1 beta polypeptide chain