major histamine complex

Question 1

recognition of antigens by B cells and T cells

Answer 1

In adaptive immune system, for appropriate response to a foreign antigen

lymphocytes must recognize antigen

stimulated to divide and differentiate

Question 2

antigen recognition

Answer 2

On B cells is mediated by surface immunoglobulin (BCR)
BCR binds to native (unprocessed) antigen on pathogens

On T cells is mediated by T cell receptor (TCR)

Question 3

what is the only thing t cells recognize

Answer 3

parts of antigens that are processed and expressed on host cells

Question 4

what do cells display on their surface

Answer 4

peptide fragments derived from the pathogen’s proteins

Question 5

pathogen-derived peptides delivered to and presented at the cell surface by specialized glycoproteins known as ….. molecules

Answer 5

major histocompatibility complex (MHC)

Question 6

Major histocompatibility complex

Answer 6

1. MHC proteins are encoded in a large cluster of genes on chromosome 6
2. First identified in transplantationMHC antigens on transplanted tissue are recognised by recipient’s immune system rejection
3. In humans MHC molecules also referred to as HLA(Human Leucocyte Antigens)
4. T cells recognise combination of MHC molecule and small peptide fragment of antigen

Question 7

how many MHC families are there

Answer 7

2

Question 8

how many members does each family of MHC have

Answer 8

3

Question 9

MHC Class 1

Answer 9

HLA-A, HLA-B, and HLA-C

Question 10

MHC Class 2

Answer 10

HLA-DP, HLA-DQ, and HLA-DR

Question 11

MHC class 1 expression pattern

Answer 11

expressed on all nucleated cells including leucocytes

Question 12

MHC class 2 expression pattern

Answer 12

expressed only on leucocytes which present antigen T cells
i.e. Antigen-presenting cells

Question 13

MHC clinical implications

Answer 13

Transplantation
e.g. kidney transplants
skin grafts
bone marrow

Question 14

what is the role of MHC1?

Answer 14

show self antigens on cell membrane.
found on all nucleated cells.

Question 15

what is the role of MHC2?

Answer 15

show internalized pathogenic antigens on cell membrane.
go to the lymphnode to signal an adaptive immune response.

Question 16

Class 1 and Class 2 have related 3D structures but different …

Answer 16

subunits

Question 17

what do the two protein domains nearest to the membrane resemble

Answer 17

immunoglobulin domains

Question 18

what do the two domains furthest away from the membrane fold together to create

Answer 18

a long groove
- antigenic peptide binds in this groove

Question 19

explain how the MHC 3d structure is influenced

Answer 19

the major differences between MHC polymorphic variants are located in peptide-binding cleft

influences which peptides will bind

Influences the overall 3D structure of the combination of MHC and peptide that will be recognized by specific TCR

Question 20

summary

Answer 20

MHC Class I and II proteins present peptide fragments of antigens derived from pathogens to TCR on T cells
* MHC molecules are extensively polymorphic
* Through its TCR, a T cell recognizes an antigen as a peptide bound by a particular polymorphic variant of an MHC molecule. It will not recognise the same peptide bound to other MHC molecules = MHC restriction
* For successful transplantation, it is important to have a good match between MHC of the donor and the recipient
* Some MHC haplotypes predispose individuals to certain diseases
* MHC Class I and II have related structures, comprising lower Ig-like domains and upper paired domains that form a peptide-binding cleft
* MHC Class I present antigens to CD8+ cytotoxic T cells
* MHC Class II present antigens to CD4+ helper T cells