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Immunuology > Major histocompatibility complex > Flashcards

Major histocompatibility complex Flashcards

1
Q

what is needed for an appropriate response to a foreign antigen?

A

lymphocytes must recognise antigens to be stimulated to divide and differentiate

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2
Q

what does each lymphocyte have?

A

its own antigen specificity

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3
Q

what initates a primary response?

A

recognition and binding to an antigen by a specific lymphocyte

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4
Q

What does the primary response produce?

A
  • Effector cells- job to eliminate antigen

- memory cell pool

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5
Q

Describe the role of the memory cell pool.

A
  • Long lived and still specifc to antigen
  • Gone through one round of activation so during second encounter to the same antigen there is a faster and greater response which produces more effector cells and a larger memory cell pool
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6
Q

what is antigen recognition on B cells mediated by?

A

surface immunoglobulin

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7
Q

what is antigen recognition on T cells mediated by?

A

T cell receptor (TCR)

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8
Q

what do T cells only recognise?

A

antigens that are expressed on cell surfaces

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9
Q

where can antigens expressed on cell surfaces be derived from?

A
  • These antigens can be derived from pathogens that replicate within host cells e.g. viruses or intracellular bacteria
  • Alternatively these antigens may come from pathogens or their products that have been endocytosed from the extracellular fluid
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10
Q

In both T and B cell cases, what do cells display on their surface?

A

peptide fragments derived from the pathogen’s proteins

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11
Q

what can be detected by T cells?

A

presence of infected cells and foreign antigens

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12
Q

what is major histocompatibilty complex (MHC) ?

A

Specialised glycoprotein that delivers pathogen-derived peptides and presents them at the cell surface

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13
Q

where are MHC proteins encoded for?

A

large cluster of genes on chromosome 6

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14
Q

what happens when MHC antigens on transplanted tissue are recognised by recipient’s immune system?

A

rejection

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15
Q

what are MHC molecules also refereed to as?

A

HLA- human leucocyte antigens

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16
Q

what does T cells recognise ?

A

combination of MHC molecule and small peptide fragment of antigen

17
Q

what are the 2 MHC families?

A
  • class I

- class II

18
Q

what are the 3 members of Class I?

A

HLA-A, HLA-B and HLA-C

19
Q

what are the 3 members of Class II?

A

HLA-DP, HLA-DQ and HLA-DR

20
Q

what makes each class distinct?

A

distinct subunit compositions but similar three-dimensional structures

21
Q

where is class I expressed?

A

expressed on all nucleated cells including leucocytes

22
Q

where is class II expressed?

A

expressed only on leucocytes which present antigen to T cells e.g. monocytes, marcophages

23
Q

what does each individual express?

A

two forms of each protein co-dominantly - one derived

from the mother, one from father

24
Q

What are clinical implications of MHC?

A
  1. Tissue grafting e.g. kidney transplants, skin grafts
  2. Certain HLA types are predisposed to certain diseases
  3. Forensic medicine
25
Q

Describe the structure of class I.

A
  • alpha chain

- B2 micro-globulin

26
Q

Describe the structure of class II.

A
  • two transmembrane polypeptides
  • alpha chain
  • beeta chain
27
Q

what is the main difference between MHC class I and II?

A

peptide-binding cleft is more open that in MHC Class I

28
Q

how are peptides anchored into grooves?

A

formed by upper two domains by hydrogens bonds

29
Q

What are functions of class I and class II MHC proteins?

A
  • T cells only see antigen in association with MHC proteins
  • MHC present antigenic peptides to T cells
  • Any one type of MHC molecule can present many peptides with similar structure
30
Q

what does MHC Class I present and describe the process?

A

Peptides to Tc (cytotoxic) cells

  • viral and cellular proteins broken down into peptides
  • MHC complexes cover cell surface
  • cytotoxic T cell recognises viral protein in MHC display as foreign and destroys cell
31
Q

what does MHC Class II present and describe the process?

A

peptides to Th (helper) cells

  • foreign body taken in during phagocytosis into processing compartment with limited proteolysis
  • MHC class II and processed peptide on surface of cell and recognised by Th cells which also call for help from B cell

Immunuology (10 decks)

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