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SFM own flashcards > Immunology > Flashcards

Immunology Flashcards

1
Q

What are the 2 primary lymphoid organs

A

bone marrow

thymus

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2
Q

what does the bone marrow do

A

produces haematopoeitic stem cells- T cells, B cells, NK cells
RBCs are produced by these stem cells

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3
Q

what happens in the thymus

A

positive and negative selection of T cells

so maturation of T cells occurs here

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4
Q

what happens to the thymus as you get older and what problem does this cause in elderly

A

it dissolves

the elderly therefore can’t produce antibodies to fight infection as easily because T cells can’t mature quickly

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5
Q

what are the secondary lymphoid organs

A

lymph node

spleen

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6
Q

what is the spleen and it’s function in immunological response

A

it’s an organ found top L of abdomen
its role is to filter blood but it is also involved in the immune response
a lot of blood passes through the spleen- captures antigens in blood

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7
Q

what 2 things is the spleen composed of

A

red pulp- has red blood cells
white pulp- has immune cells- T and B cells

white pulp in the middle surrounded by red pulp and then immune response kicks in either CD4- B cells- antibodies or CD8- apoptosis

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8
Q

Lymph nodes

A

collects antigens from tissues

an area where B and T cells can talk to each other

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9
Q

where does the positive and negative selection process occur

A

in the thymus (lymphoid organ)

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10
Q

characteristics of starting cell that enters the thymus for positive and negative selection process

A

it is naive, undifferentiated

double +ve ie CD8 and CD4

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11
Q

what is the first stage of positive and negative selection

A

this is the positive selection part
so after the naive cell enters the thymus it encounters MHC1 and MHC11 receptors on B cells and interacts with the self antigen on them
those that interact with appropriate affinity (ie those that don’t react move on as shouldn’t have high affinity for SELF don’t want to kill it)
those that don’t APOPTOSIS

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12
Q

What is the second stage of positive and negative selection

A

now the negative selection part…
the cells that passed positive selection are then shown self-antigen on antigen presenting cells
this is the T cell receptor and MHC1 or MHCII (t and b cell speaking)
if the interaction is too strong the cells die (apoptosis- happens to most cells)

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13
Q

what happens to leftover cells after positive and negative selection

A

the leftover cells won’t have reacted to any self-antigens and therefore NORMAL
can enter the systemic circulation
they lose either one of their CD4 or CD8 expression so differentiate before they leave the thymus

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14
Q

Natural killer cells

A

2 types - pure innate and innate/adaptive
NK cells detect foreign antigens
they don’t engulf the stricken cell but instead attach to it and release PERFORIN and GRANZYME into the cell and induce apoptosis
you can’t educate it/make it better over time
the innate/adaptive express a T cell receptor on the NK cell so are said to be partly adaptive

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15
Q

what is the complement fixation test

A

a test for infection with a microorganism

detect the presence of either specific antibody or specific antigen in a patient’s serum,

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16
Q

missing self hypothesis

A

every cell in our bodies expresses MHCI receptor on their surface
viruses can remove these MHC1 receptors however

so NK cells roam through the body looking out for these receptors to know that the cell is ‘self’ and normal
if it can’t see the MHC1 (virus took it away) then it becomes activated and releases perforin and granzyme- apoptosis
they help with tumour surveillance by killing cancerous cells

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17
Q

difference between apoptosis and cell lysis

A

lysing a virus-infected cell would only release the virions (splits the cell and kills it but releases contents

whereas apoptosis leads to destruction of the virus inside.

18
Q

what do Natural killer cells try to contain

A

they try to contain viral infections while the adaptive immune response is generating antigen-specific cytotoxic T cells that can clear the infection.

19
Q

describe the innate response

A
  • present at birth
  • 1st line of defence (if physical barriers fail)
  • no immunological memory created, no education- can’t get better over time
  • occurs in the same way at the same speed every time
  • may completely eliminate the agent before the specific adaptive immune response is called upon
  • also interacts with the adaptive immune response, aiding its activation and modulating the response.
20
Q

what are the key cells involved in innate immunity

A

phagocytes- dendritic cells (in the tissues/lymphoid tissues)
macrophages- phagocytes- key to activating adaptive
complementary proteins (the complement system) - link between innate and adpative
inflammatory mediators (chemicals like histamine)
white blood cells like neutrophils, eisonophils, basophils, mast cells, NK cells

21
Q

what 4 WBCs involved in innate response are granulocytes

A

neutrophils- arrive first at site of infection- contain granules and are also phagocytic
basophils- contain cytotoxic granules
eisonophils- phagocytic
mast cells- histamine

22
Q

which cells from the innate system are responsible for speaking to the adaptive system and activating it and how do they do this

A

macrophages or dendritic phagocytic cells
they present the antigen of the pathogen to the T cells in adaptive immunity
they are called antigen presenting cells
can present to both types of T cells

however tend to present antigens originating inside the cell to cytotoxic T cells so apoptosis can be induced and it can kill virus inside cell
and antigens on surface are presented to T helper cells that go on to activate B cells (antibody production), NK T cells and macrophages

23
Q

why is the adaptive system brought in after innate

A

the innate phagocytes will try to consume and destroy the pathogen but if it can’t they will recruit help and activate adaptive system (can take weeks however) and in the meantime innate will try to contain infection

24
Q

what are the 2 types of T helper cells and what are their functions

A

Th1 and Th2 (converted into B cell)

present the antibody to a B-cell which then produces antibodies

25
Q

what happens when a cytotoxic T cell is activated from being presented a foreign antigen on infected phagocyte (from innate)

A

it becomes activated and goes and finds pathogen with same antigen as was presented to it
it then induces apoptosis
creates pores in the membrane and releases cytotoxic chemicals- perforin and granzyme into the cell killing the infection inside the cell so it is not released when the cell dies

26
Q

what happens when an APC (from innate) presents antigen to a T helper cell

A

T helper cell becomes activated it goes and talks to B cell and presents the antigen on a T cell receptor to the B cell’s MHCII receptor.
This activates the B cell

27
Q

what 2 things happen upon activation of B cells

A
  1. The B- cell goes off around the blood to find the whole pathogen for this specific antigen to try and kill it
  2. B-cell differentiates into memory B-cells called PLASMA cells that mass produce antibodies to fight the infection quickly - better on reexposure as well
28
Q

why might a booster vaccine be needed to replenish plasma cells

A

sometimes plasma cells made by B cells don’t make enough antibodies or the antibodies sometimes reduce in numbers- die - over time

29
Q

what 3 things can happen from the antibodies produced by plasma cells

A

they can:-
neutralise the pathogen
opsonise the pathogen
activate complement

30
Q

neutralise the pathogen- what does this mean?

A

antibodies bind to the antigens on a pathogen and neutralise it which prevents bacterial adhesion to cells or surfaces ie prevents colonisation in body

31
Q

opsonise the pathogen- what does this mean?

A

they can coat the pathogen in antigens to make it easy to detect by phagocytes

32
Q

activate complement- what does this mean?

A

antibodies can opsonise pathogen as well as lysing pathogen- self destruct break down cell membrane

33
Q

what are the 5 classes of antibodies produced by plasma cell

A 
IgG- good opsoniser
IgA- resistant to stomach acid- good at protecting surfaces from things like colonisation
IgM- fixing complement and opsonisation
IgE- allergies- histamine
IgD- unkown
34
Q

describe the antibody structure

A

variable region- where the antigen binds
Y shaped- light chain and heavy chain on top bits
called gamma immunoglobulin

35
Q

what are cytokines? and what are also referred to as

A

Chemicals used by cells to communicate with other cells- they are mediators of the immune system

interleukins

36
Q

what are the 3 types of cytokine action

A

paracrine- release cytokines that communicate with nearby cell
endocrine- release cytokines into circulation that reach a distant cell
autocrine- release cytokines that act on same cell

37
Q

name of the 4 important interleukins

A

IL-4
IL-17
IL- 21
IFN gamma

38
Q

difference between variable and constant region in antibody structure

A 
constant- same for all antibodies of the same class
variable- differs between different B cells
39
Q

what clinical problem can mast cells cause

A

anaphylaxis as it releases histamine which causes inflammatory response

40
Q

complement system

A

group of proteins in serum
when activated cause complement cascade which results in the following effects:-
- cell lysis- membrane broken down
- chemotaxis- cytokines/chemokines that bring immune cells to the site of infection
- agglutination- brings pathogens to same area- easier to fight
- opsonisation

41
Q

what are the 2 pathways that activate the complement system

A

classical and alternative

they start differently but have same outcome- lysis/opsonisation

SFM own flashcards (17 decks)

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