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Flashcards in Major histocompatibility complex Deck (31)
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1

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

lymphocytes must recognise antigens to be stimulated to divide and differentiate

2

what does each lymphocyte have?

its own antigen specificity

3

what initates a primary response?

recognition and binding to an antigen by a specific lymphocyte

4

What does the primary response produce?

-Effector cells- job to eliminate antigen
-memory cell pool

5

Describe the role of the memory cell pool.

-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

6

what is antigen recognition on B cells mediated by?

surface immunoglobulin

7

what is antigen recognition on T cells mediated by?

T cell receptor (TCR)

8

what do T cells only recognise?

antigens that are expressed on cell surfaces

9

where can antigens expressed on cell surfaces be derived from?

-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

10

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

peptide fragments derived from the pathogen's proteins

11

what can be detected by T cells?

presence of infected cells and foreign antigens

12

what is major histocompatibilty complex (MHC) ?

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

13

where are MHC proteins encoded for?

large cluster of genes on chromosome 6

14

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

rejection

15

what are MHC molecules also refereed to as?

HLA- human leucocyte antigens

16

what does T cells recognise ?

combination of MHC molecule and small peptide fragment of antigen

17

what are the 2 MHC families?

-class I
-class II

18

what are the 3 members of Class I?

HLA-A, HLA-B and HLA-C

19

what are the 3 members of Class II?

HLA-DP, HLA-DQ and HLA-DR

20

what makes each class distinct?

distinct subunit compositions but similar three-dimensional structures

21

where is class I expressed?

expressed on all nucleated cells including leucocytes

22

where is class II expressed?

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

23

what does each individual express?

two forms of each protein co-dominantly - one derived
from the mother, one from father

24

What are clinical implications of MHC?

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

25

Describe the structure of class I.

-alpha chain
-B2 micro-globulin

26

Describe the structure of class II.

-two transmembrane polypeptides
-alpha chain
-beeta chain

27

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

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

28

how are peptides anchored into grooves?

formed by upper two domains by hydrogens bonds

29

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

-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

what does MHC Class I present and describe the process?

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