Adaptive immunity Flashcards

1
Q

true or false: antigens activate T cells

A

false - antigen presenting cells do

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2
Q

what are intracellular and extracellular microbes

A
intracellular = microbes that divide inside cells. they are usually viruses 
extracellular = microbes which divide outside of cells. these are mainly bacteria
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3
Q

where are antigen presenting cells located

A

in the skin (SALT), mucus membranes (GALT, BALT), lymph organs and in the blood

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4
Q

how do antigen presenting cells capture the pathogen

A

by phagocytosis (may require opsonisation) of whole microbes or macropinocytosis of soluble particles

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5
Q

how do antigen presenting cells detect the pathogens

A

with their PRRs which are specific to the PAMPs on the microbes

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6
Q

name 4 different APC

A

dendritic cells - found in lymph nodes, mucus membranes and blood and present to naive T cells
langerhans cells -found in the skin and present to naive T cells
Macrophages - found in various tissues and present to effector T cells
B cells - found in lymphoid tissue and present to effector and naive T cells

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7
Q

what are naive T cells

A

T cells which havent yet been activated by APC

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8
Q

what type of immunity is initiated by extracellular microbes

A

humoral immunity (involving antibodies, complement and phagocytosis)

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9
Q

what type of immunity is initiated by intracellular microbes

A

cell dependant immunity (involving cytotoxic t lymphocytes, antibodies and macrophages)

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10
Q

what is required for antigen presentation

A

major histocompatibility complex

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11
Q

what is MHC

A

cell surface proteins which recognise and bind to antigens and display them on their surface for recognition by T cells

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12
Q

where are class I and class II MHC molecules found

A
  • found on all nucleated cells (class I)

- found on dendritic, macrophages and B cells (class II)

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13
Q

what genes code for class I MHC molecules

A

HLA A, HLA B and HLA C

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14
Q

What genes code for class II MHC molecules

A

HLA DR, HLA DQ, HLA DP

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15
Q

true of false - classes I and II MHC molecules are co-dominant

A

true - this increases the number of different MHC molecules

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16
Q

what does it mean by saying that the MHC molecules have polymorphic genes

A

there are different alleles among individuals which increases presentation of different antigens

17
Q

what peptides do MHC class I present

A

self and non-self peptides from intracellular microbes

18
Q

what peptides do class MHC class II present

A

non self peptides from extracellular proteins

19
Q

describe the structure of MHC class I molecules

A

1 heavy/alpha chain and 1 beta chain

groove which allows a peptide to bind to

20
Q

describe the structure of MHC class II molecules

A

2 chains containing alpha and beta
chains are the same length
groove for the peptide to bind to

21
Q

why is the peptide binding cleft variable

A

so that lots of different proteins can bind

22
Q

what T cells recognise MHC class I molecules

A

CD8+ (cytotoxic t - kill infected cells)

23
Q

what T cells recognise MHC class II molecules

A

CD 4+ (T helper - activates B cells and macrophages)

24
Q

which molecules go through the endogenous pathway and describe this pathway

A

intracellular - proteasomes degrade the virus into fragments. Peptides are taken to ER where they bind to MHC1 proteins before being transported to cell surface membrane. Once here they can be recognised by T cells

25
Q

which molecules go through the exogenous pathway and describe this pathway

A

extracellular - the antigen is taken up into a vesicle which fuses with a lysosome to form an endosome when the proteins are broken down. The peptide fragments bind to the MHC II molecules and move to the cell surface membrane

26
Q

true or false - peptides from the same microbes are presented by the same MHC molecule

A

false

27
Q

what are elite controllers

A

patients who can control viral replication - they have the slow progressor type of the HLA B gene and so give an effective T cell response. Others have rapid progressor HLAB gene which gives poor recognition by T cells

28
Q

what are the clinical problems of MHC molecules

A
  • major cause of organ transplant due to mismatch of molecules in a allograft
  • cause graft versus host reaction
  • associated with autoimmune disease
29
Q

what autoimmune diseases are MHCs associated with

A
  • ankylosing spondylitis (HLA B)

- insulin dependant diabetes mellitus (HLA DQ)

30
Q

through which receptors do the MHC molecules activate T cells

A

T cell receptors

31
Q

what different CD4+ T cells are acitavted and what effects do they have

A
  • TH2 CD4+ = activates eosinophils, B cells and Mast cells

- TH17 CD4+ = activates neutrophils

32
Q

what is the main antibody produced in the primary and secondary response

A
primary = IgM
secondary = IgG
33
Q

describe the changes in the antibodies IgG and IgM during an immune reaction

A

during the first response there are high levels of IgM and low levels of IgG
this is reversed in the secondary response

34
Q

what is the function of IgG

A
  • enhances phagocytosis
  • activates complement cascade
  • gives neonatal immunity
  • neutralises toxins and viruses
35
Q

what are the functions of IgE

A
  • allows for mast cell degranulation in allergic responses
36
Q

what is the function of IgM

A

complement activation

37
Q

what is the function of igA

A

mucosal immunity