IC5 Flashcards
cellular component for innate immunity
1) phagocyte (neutrophil, macrophage)
2) NK cell
3) dendritic cell
4) Mast cell
humoral component for innate immunity
cytokines, complement proteins
cellular component for adaptive immunity
T cell, B cell
humoral component for adaptive immunity
cytokines, antibodies
general features of antibodies
- intra and inter disulfide bonds to maintain 3d configuration
- glycosylation in Fc domain
- 2 Fab 1 Fc
number of CDR on 1 antibody
3 CDR on light chain, 3 CDR on heavy chain = 6 CDR per Fab arm = 12 CDR per antibody
properties of antibody
1) antigen affinity
- single antigenic site
2) antibody avidity
- multiple antigenic site
3) antibody specificity
- low specificity = cross reactivity
T cell receptor
- alpha + beta chain
- components of both chains:
1) extracellular domain (glycosylated): variable region bind to antigen), constant region (cysteine residue, form disulfide bond to link both chians)
2) transmembrane region
3) short cytoplasmic tail
why T cell receptor not enough to activate T cell?
cytoplasmic tail too short to mediate signal transduction for T cell activation
CD3 adaptor proteins
- 6 monomers dimerise -> 3 invariant CD3 dimers -> octameric complex
ITAM
- each TCR 10 ITAM
- tyrosine phosphorylated -> downstream T cell signaling -> activation
antibody vs T cell receptor (no. of CDR)
antibody: 12 CDR
T cell receptor: 6 CDR
process of B cell activation
1) progenitor B cell in bone marrow rearrange Ig genes -> clones of immature B cell expressing B cell antigen receptor
2) B cell leave bone marrow -> circulate blood stream/lymphoid tissue
3) encounter pathogenic antigen -> activate -> mature -> produce 1st response antibody IgM
4) gene arrangement of constant region in Fc domain of IgM -> class switching to IgG
5) B cell undergo gene arrangement to VL and VH of IgG gene -> different hypervariable CDR w different antigen specificity -> produce IgG with different CDR
development of T cells
1) T lymphocyte progenitor travel from bone marrow to thymus for development into T lymphocytes
2) T cells localised in secondary peripheral lymphoid tissue -> interact & respond to antigens
how does T cells have memory
1) effector T cell die after interacting with pathogen
2) Remaining antigen-specific T cells differentiate into memory T cells
MHC class I
- location: all nucleated cell & platelets, absent in RBC
- bind to peptide fragment of endogenous antigen
- present antigen through peptide-MHC I on cell surface
- present antigen to CD8+ cytotoxic T cell
examples of endogenous antigens
- normal self antigen
- viral component from virus-infected cell
- neoantigen (Cancer)
MHC class II
- location: APC (macrophage, dendritic cell), B cell
- bind to peptide fragment of exogenous (foreign) antigen
- present antigen through peptide-MHC II on APC surface
- present antigen to CD4+ helper T cell
regulation of MHC molecules
- expression directly proportionate to T cell activation
- regulated by cytokines
1) IFN alpha
2) IFN gamma
characteristics of MHC
1) polygenic (multiple genes)
- express different peptide binding specificities
- means different set of MHC = present different antigen = broad coverage
2) polymorphic
- each gene different alleles = broad coverage
general properties of cytokines
- glycosylated for action/half life
- short half life prevent uncontrolled action
- act short range (paracrine/autocrine)
cytokine classes - interferons - source
produced by cells in response to viral infections, tumours, other biological inducers
cytokine classes - interferons - function
1) promote antiviral state in neighbouring cells
2) help regulate immune response, growth & differentiation
cytokine classes - interferons - type I
1) IFN alpha
- recombinant IFN alpha protein for upregulation of immune system for antiviral and/or anticancer therapy
2) IFN beta
- expressed by most somatic cells
- effective treatment for multiple sclerosis (inhibit IFN gamma)
cytokine classes - interferons - type II (IFN gamma)
- produced by T cells
- immunomodulatory
** activate resting macrophage & monocyte -> increase phagocytic activity
** induce macrophage -> express cytokine (IL-2, TFN-alpha), MHC, immunoglobulin Fc receptor -> immunostimulation
cytokine classes - interleukin - source
leukocytes
cytokine classes - interleukin - function
1) Affect growth & differentiation of hematopoietic & immune cells
2) regulate immunity, inflammation, haematopoiesis
cytokine classes - interleukin - types
1) IL-2
- T cell growth factor
- synthesised & secreted by T cells
- immunomodulatory properties
2) IL-11
- thrombopoietic growth factor
- produced by fibroblast & bone marrow stromal cell
- stimulate proliferation of haemotopoietic stem cell + induce megakaryocyte maturation -> increased platelet formation
cytokine classes - chemokines
stimulate leukocyte chemotaxis & Activation
cytokine classes - tumour necrosis factor (TNF)
- pro inflammatory & pro apoptosis
- contribute to insulin resistance
cytokine classes - haemotopoeitic growth factor - general
- single chain glycoprotein
- used to restore deficiency from chemo/radio therapy
cytokine classes - haemotopoeitic growth factor - types
1) colony stimulating factor (CSF)
- stimulate cellular division and differentiation of blood cells from bone marrow precursors
2) erythropoeitin, interleukin
- promote haematopoeisis
polyclonal antibodies - antiserum - general
- usage: passive immunisation
- disadvantages: immunogenicity
polyclonal antibodies - antiserum - production method
1) collect whole blood from animal
2) let blood clot/add coagulant
3) remove clotting factor
4) Centrifugation -> separate cellular component -> serum obtained as supernatant
5) purification
- eliminate serum protein
- enrich fraction of Ig that react w target Ag
features of monoclonal antibodies (mab)
1) high specificity
- 1 B cell clone only recognise 1 epitope
- used in recombination protein purification work
2) high homogeneity
- effects highly reproducible
- uses: commercial development (test kit), research
development process of mab: 1) murine mab
- induce immunogenicity: human-anti-mouse antibody (HAMA) response
- shorter half life, X trigger some effector functions
development process of mab: 2) chimeric mab
- CL, CH of Fc and Fab -> immunogenicity
- replace AA in CH and CL that are not essential for antigen binding w human sequences to reduce immunogenicity & still retain antigen selectivity & affinity
development process of mab: 3) humanised mab
- replace all moues AA sequence except hypervariable CDR domains of Ig (inside VH and VL) in chimeric mab
development process of mab: 4) recombinant human mab
- genetically engineer mammalian host cell so everything human -> X immunogenicity
- problem: $$$$, X remove impurities from mammalian host cell
when do you not require Fc domain
1) enzyme inhibition
- antagonism of enzyme action by binding to enzyme active site
2) neutralise receptor ligands (hormones/cytokines)
3) counteract overproduction of cytokines
4) neutralise toxin
types of antibody derivatives
1) Ig conjugate
- conjugated to cytokine/toxin/radioisotope -> antibody endocytosis into cell -> conjugate exert lethal effect
2) F(ab’)2
- only 2 same Fab arm, X Fc domain
3) ScFv
- synthetic
- single polypeptide chain of VL and VH
4) biospecific
- 2 different Fab arms
- bring 2 antigens close together
- used for cancer treatment
5) triomabs
- biospecific + Fc domain
6) defucosylated Abs
- remove fucose from N-glycan at Asn297 -> enhanced affinity towards FcgammaRIII -> increase ADCC induction by effector cell
Tumour-infiltrating lymphocyte (TIL) therapy - general
- autologous
- more for solid tumours
Tumour-infiltrating lymphocyte (TIL) therapy - process
1) take out patient tumour cell
2) remove lymphocyte from blood vessel in tumour
3) TIL expanded and reintroduced into patient
Tumour-infiltrating lymphocyte (TIL) therapy - benefits
safe
Tumour-infiltrating lymphocyte (TIL) therapy - limitations
- sometimes excised tumour mass no/little TIL
- varying antigen specificity -> X specific/lethal enough to kill cancer
- X high affinity
T cell receptor engineered T cell (TCR-T) therapy - process
insert Valpha & Vbeta tumor antigen specific gene clones into vector -> transduce T cells isolated from patient’s peripheral blood
T cell receptor engineered T cell (TCR-T) therapy - table of summary
1) what changes
- express specific TCR that recognise cancer specific antigens
2) TCR
- full TCR complex but modified to recognise cancer specific antigen
3) antigen recognition
- antigen presentation by MHC complex
- dependent on specific HLA type
4) types of tumours
- solid & haematological tumour
T cell receptor engineered T cell (TCR-T) therapy - advantages
more effective than CAR-T
T cell receptor engineered T cell (TCR-T) therapy - disadvantages
- limited for use in patient with specific MHC/HLA allele recognised by TCR
- not as safe as TIL
** on target toxicity: T cell target normal tissue
** off target toxicity: T cell not specific
** cytokine storm
Chimeric antigen receptor T cell (CAR-T) therapy - process
withdraw T cell from patient -> transduce T cell by vector carrying CAR gene -> T cell express CAR on surface -> expansion -> release back into patient to target cancer cell
Chimeric antigen receptor T cell (CAR-T) therapy - developmental process
1) gen 1
- extracellular: single chain variable fragment connecting VH & VL
- intracellular: CD3 complex (not full TCR)
2) gen 2
- same extracellular
- intracellular: CD3 + CD28 (costimulatory)
- more potent anti tumour effect but in vitro
3) gen 3
- same extracellular
- intracellular: CD3 + CD28 + 4-1BB (costimulatory)
4) gen 4
- similar to gen 3 but additional transgene that express cytokines
** cytokines autocrine +/- paracrine effect
** CAR-T activation -> activate transgene -> release cytokines (IL-2) -> activate more T cells at target site
** only gen that target anti-negative cancer cells (X release antigens) cuz IL-2 act on endogenous T cells -> target other cells
Chimeric antigen receptor T cell (CAR-T) therapy - summary table
1) change what
- express CAR on TCR surface to recognise specific antigen on cancer cell surface
2) TCR
- replaced w synthetic CAR -> X full TCR complex
3) antigen recognition
- X HLA restricted
- only bind directly to surface antigen
4) type of tumours
- more effective for haematological tumours *cuz X get through intra tumoural space)
Chimeric antigen receptor T cell (CAR-T) therapy - advantages
X TCR complex = recognise antigen wo MHC protein
Chimeric antigen receptor T cell (CAR-T) therapy - disadvantages
- scFv guide CAR-T cell into antigen-independent mechanism = failed therapy
- less effective than TCR-T
- adverse effect
** on target off tumour toxicity: B cell aplasia
** off target toxicity
** cytokine storm
immune check point inhibitor - CTLA-4
- APC present MHC antigen -> bind to TCR
- CD80/CD68 on APC bind to CD28 -> stimulate CD28 to release cytokines -> T cell activation
- CTLA4 compete w CD28 -> no activation when bind to CD80/CD86
immune check point inhibitor - PD-1
PD-L1 or PD-L2 bind to PD-1 on T cell -> suppress T cell activity
limitations of immune checkpoint inhibitors
- transient efficacy
- X all cancer patients show response
- possible immune-related AR
types of cancer vaccine - cell vaccine
1) tumour cell vaccine
- antigens expressed by tumour cell induce patient T cells
2) dendritic cell vaccine
- tumour antigenic proteins/peptides or tumour cell loaded on DC -> adminsitered to induce T cell
types of cancer vaccine - protein/peptide
- antigenic peptide fragments derived from tumour-associated antigens -> recognised by T cell -> Activation
- limitations: not strong immune response
** X include neoantigens
** X bind to MHC class II = X CD4+ help
** antigenic peptide of short chain bind to any cell wo triggering further process = induce anergy (X immune response) = immune tolerance BUT can be rectified if manufacture longer peptide chains
types of cancer vaccines - nucleic acid
- RNA/DNA w viral vector/non vector based system
- considerations:
1) DNA: risk of carcinogenicity if insertion of DNA gene cause mutation
2) RNA: X risk of carcinogenicity but problem of formulation stability/stability upon adminsitration
types of CDR
1) CDR 1 & 3: bind to peptides
2) CDR 2: bind to MHC
