l1 Flashcards by J A

what is Adaptive immunity

Protects us from repeat infections with the same pathogens

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Adaptive immunity IMPROVES WHAT

Improves the efficacy of the innate immune response

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what does it foucs on

Focuses a response on the site of infection and the organism responsible

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what is its key fetaure

Has memory

Once the immune system has recognised and responded to an antigen, it exhibits “memory”

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the drawback

Needs time to develop

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the memory is more or less rapid

Memory responses are characterised by a more rapid and heightened immune reaction that serves to eliminate pathogens fast and prevent diseases.

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basis of what

Memory responses are characterised by a more rapid and heightened immune reaction that serves to eliminate pathogens fast and prevent diseases.

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is it long lived

yes

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The two types of Adaptive immune response

The ‘cell-mediated’ Response

The ‘humoral’ Response

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The ‘cell-mediated’ Response

function

T Cells
Two roles:
Produce cytokines to help shape immune response (CD4)
Kill infected cells (CD8)

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The ‘humoral’ Response

function

Produce Antibody

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Epitope

The region of an antigen which the receptor binds to.

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T cells recognise what

linear epitopes
in the context of MHC
primary structure

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Antibodies recognise

Structural Epitopes

folding/teriarty

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what is clonal expansion

multiple copies of the same cell

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To deal with antigen diversity we need to

encode a massive Repertoire of lymphocytes receptors

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Antigen receptor diversity is generated by

recombination

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Functional genes for antigen receptors do not exist until they

are generated during lymphocyte development

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Each BCR receptor chain

is encoded by

separate multigene families on different chromosomes

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Immunoglobulin gene rearrangement

During B cell maturation these gene segments are rearranged and brought together

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Immunoglobulin gene rearrangement generates

diversity of the lymphocyte repertoire

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The variable region made by

gene reassortment

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MHC

plays a central role in defining self and not self

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function of mhc

Presents antigens to T cells

Critical in surgery- and donor matching

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MHC class I expressed by

all nucleated cells, although at various levels

structure og mhcI

Has a single variable alpha chain plus a common beta-microglobulin

MHC class II: normally only on

“professional” antigen presenting cells.

structure

Has 2 chains, alpha and beta

what is mhc coded by

HLA genes

Expression

is co-dominant | polygenic

CD8 molecule binds to

MHCI

and cd4

MHCII

MHCI only process antigens from

Intracellular pathogen/antigen

procseed where

Cytosol

MCHII processess what

Extracellular pathogen/ Antigen

where

Endosomes

T Helper cells produce

cytokines (a family of inflammatory mediators).

Cytokines have and influence

diverse actions on a wide range of cells | Cytokines influence the outcome of the immune response

Th1

Pro-Inflammatory | Boost Cellular Immune Response

Th2

Pro-Allergic

Th17

Pro Inflammatory | Control Bacterial and Fungal Infection

thF

MAKE BETTER ANTIBODIES

Cytotoxic T cells kills how

targets by programmed cell death = apoptosis

what do granzymes do

cd8 makes pore injects granzymes cell death

perforin function

Perforin molecules polymerise, form pores

what do cd8 store

store perforin, granzymes

how cd8 scan | and virus exposes itself

In uninfected cells, MHCI molecules show self peptides The CD8 cell scans cells, looking for non-self MHC. Not finding any, it does nothing. A virus infects the cell and releases its contents The cell now starts making viral proteins It displays these as non-self MHC The CD8 cells detects the non-self MHC and attacks The CD8 cell kills the virally infected cell

3 key features of b cell

Make Antibody Recognise soluble antigen Need help from other sources to produce antibody (normally T cells)

strcuture of antibodies

Y have 2 heavy abd 2 light chain constant and variable region- how it recognises diff antigens

3 Core protective roles:

Neutralisation Opsonisation Complement activation

Neutralisation

binds to active site on bac or virus preventing it having its function response e.g. stop entering

Opsonisation

make it more atrractive to bieng phagocyosis of macrophages

Complement activation

cascade of events leading to death of anything that the antibody is bound to

what defines the class

constant region

how many classess

igG

high opsonization and nuetrilisation | 4 subclasses

IgM

produces first upon antigen invasion

IgA

expressed in mucousal tissue forming dimers after secreation

IgD

unknown function

IgE

involved in allergy

Memory B cells

ready to prevent repeat infections

The BCR made from

Surface bound antibody – encodes the antibody the cell will make same antibody that is secreated

BCR have a unique binding site which bind to a portion of the antigen called

antigenic determinant or epitope

when is it made

before the cell ever encounters antigen

how many identical copies of bcr

thousounds

b vs t

b dont need anything to present antigen

Naïve antigen-specific lymphocytes (B or T) cannot be activated byantigen alone

antigen alone | Naïve B cells require accessory signal

what are the accessory signal

Directly from microbial constituents | From a T helper cell

How is antibody production by B cells achieved?

Thymus-dependent Thymus-independent

Thymus-independent antigens

Directly activate B cells without the help of T cells Only IgM No memory

STRCTURE

Often polysaccharide, needs to have a repetitive structure, e.g. bacterial surface sugars

The second signal required is provided by

microbial PAMP, e.g. LPS

Thymus-dependent | process of t cell activating b cells

B cell activation by T cells The membrane bound BCR recognises antigen The receptor-bound antigen is internalised and degraded into peptides Peptides associate with “self” molecules (MHC class II) and is expressed at the cell surface This complex is recognised by matched CD4 T helper cell B cell activated

dc vs b

dc more broad in terms of antigen