Table of Contents
B LYMPHOCYTES ... 3
B cells: ... 3
B cell receptor diversity: ... 4
Antibody: ... 4
Antibody gene rearrangement and B cell maturation: ... 6
Responses to antigen: ... 7
Polyclonal antibodies: ... 8
Monoclonal antibodies: ... 9
Making vaccine: (bNAbs) ... 12
Primary immunodeficiencies, PIDs: ... 14
X-linked agammaglobulinaemia (XLA): ... 15
Common Variable Immunodeficiency (CVID): ... 16
Hyper-IgM (HIGM) syndrome: ... 16
Severe combined immunodeficiency (SCID): ... 17
RHEUMATOID ARTHRITIS ... 18
The Synovium ... 18
Arthritis: ... 19
Rheumatoid arthritis: ... 19
Clinical manifestation of RA ... 25
Bones: ... 27
Osteoarthritis: ... 29
Treatment of RA ... 29
Clinical trial design of RA ... 34
PANDEMICS - COVID ... 35
Coronavirus ... 35
SARS-CoV-2 ... 35
PANDEMICS - HIV ... 40
Virology ... 40
HIV Lifecycle ... 40
Immunology ... 41
Chronic immune activation ... 43
Treatment ... 43
Prevention ... 44
HIV Vaccination ... 44
HIV Cure ... 45
PANDEMICS - MALARIA ... 46
Life cycle ... 46
Virulence and immune escape ... 47
Types of vaccine: ... 48
Malaria diagnosis: ... 48
CYSTIC FIBROSIS ... 50
Introduction ... 50
Molecular basis of CF ... 50
Genetic, Environmental of cystic fibrosis ... 53
Cystic Fibrosis in LUNG ... 54
Cystic Fibrosis is a multi-system disorder ... 58
Current and future therapies in CF ... 61
TYPE 1 DIABETES ... 65
Introduction ... 65
Regulation of glucose homeostasis ... 66
Diagnosis: ... 69
Type 1 vs Type 2 diabetes: ... 71
Pathogenesis ... 71
Research into T1D ... 72
Insulin treatment ... 74
B LYMPHOCYTES
B cells:
- All lymphocytes (B,T,NK cells) descend from common lymphoid progenitor (CLP) - B cells develop in bone marrow, throughout life -> periphery circulation
- To make antibody:
o
Recognize antigen via immunoglobulin on surface (B-cell receptor)
o
Breakdown antigen and represent to T-cells as peptides on surface MHC Class II
o
T cells then provide activation signals or ‘help’ (CD40L, ICOS, cytokiens)
oAllow B-cell to differentiate to antibody secreting cells (ASCs) and memory B
cells
- Activation & Differentiation:
o
Immature B cell:
§
B cell starts life without an antigen receptor
§
During production of B cells from hematopoietic stem cells (HSC), genes encoding the B cell receptor are created -> diversity is generated
o
Mature B cell: (naïve B cell)
§
Each B cell express single species of Ig on its surface
§
B cell receptor is a surface-bound antibody
§
Immature B cells only able to leave bone marrow if express functional surface-bound antibody
§
Down-regulation of VDJ machinery (again)
§
Production of IgD by alternate gene splicing
§
Expression of both surface IgM and IgD (both with same antigen specificity)
§
B cell receptor binds antigen and is used to activate B cell -> generate plasma cell
o
Plasma cell:
§
Specialist cells that secrete one type antibody
§
Terminally differentiated cells of B cell lineage - B and T cell development:
o
B cells in bone marrow; T cells in thymus
o
Antigen receptors of B, T cells are not encoded in germline, they assembled (somatically) by combination & rearrangement of V(D)J
o
Both B, T cells undergo antigen receptor V(D)J rearrangement
§
Allow random generation of antigen receptors (B,T cell receptor)
oBoth undergo negative selection (checkpoint) to remove cells that bind with
high self affinity - Early B and T cell activation:
o
Antigen enter lymphoid organ, intact into B cell areas -> antigen processed &
presented to T cells
o
Antigen-specific B & T cells activated by antigen directly or after presentation
by Dendritic cell -> alters chemokine receptor expression: T cell express
CXCR5, B cells express CCR7
o
Chemokines & receptors direct activated B and T cell migration -> meet at boundary of T & B cells area
§
Germinal center = microstructure that forms in secondary lymphoid tissues, producing long-lived antibody secreting plasma cells and memory B cells
§
- B cells asking help from T cells:
o
Activated B cells gather, process and present antigen to T cells via MHC class II
o
After ‘recognizing’ antigen, activated T cells are co-stimulated
oCo-stimulated T cells provide ‘help’
§
CD40L/CD40: activates NFKB signaling -> induce proliferation
§
CD40L/CD40: induce AID-inducing signals
§
Differentiation signals (e.g. IL-4, IL-21)
§ If no CD4 help, B cells do nothing -> primary immunodeficiencies
B cell receptor diversity:
- Random selection and rearrangement of minigene segments in Heavy and Light chain genes (V,D,J genes)
- Independent rearrangement at Heavy and Light chain loci; and pairing of various combinations
- Imprecision of junctions: random nucleotide addition during VDJ rearrangement of H chain by TdT
- Somatic hypermutation and affinity maturation: single point mutations in
hypervariable hotspots via AID and selection of highest affinity binding receptors Antibody:
- Globular proteins found in serum, interstitial fluids, mucosal secretions - Identify and neutralize foreign pathogens e.g. bacteria, viruses
- Each antibody binds to a specific antigen - Basic structure:
o
4 chains: heavy (55kDa), light chains (25kDa) with
o2 regions: variable + constant regions (disulfide bonds)
§
Variable region (antigen binding site):
•
Antigen binding at tops of variable heavy/light
•
Composed 7 amino acid regions:
o
4 framework = scaffold
o3 hypervariable CDR
•
Hypervariable region (millions of antibodies with different antigen binding sites)
•
Determined by CDR1, CDR2, CDR3 each chain
oCDR1, CDR2 encoded in germline
oCDR3 created during rearrangement
§
Constant region:
•
Class/isotype of antibody (IgG**, IgA, IgM, IgE, IgD)
•
Each class have different distribution & effector functions (complement, ADCC, opsonization)
•
IgG – 70~85% Ig pool (10^20 in average adult human)
•
IgM – pentamer; first immune response
•
IgA – tetramer dimer; predominant in mucosal
•
IgD – unknown
•
IgE – attack parasites, allergies
•
Class switch recombination (CSR)
•
o
V(D)J rearrangement:
§
Antibody variable region is coded by V (variable) region DNA; 3 separate genes on 3 loci
•
2 L chain loci (κ, λ) + 1 H chain locus
•
H chain is rearranged first, then only one L chain (selected randomly)
o
H chain – VDJ joining
oL chain – VJ joining
•
Second chance of VJ recombination of ‘other’ L chain during Receptor Editing checkpoint
o
Prevent binding strongly with self-antigen
oActivates RAG1/RAG2
•
Transcription -> translation -> assembled antibody protein
§
Variable regions formed by somatic recombination
•
1 light + 1 heavy germline mini gene segments are somatically recombined
•
Produce unique DNA sequence encoding unique variable region
•
VDJ rearrangement of V region genes occur in pre/pro B cells - Antibodies vary due to clonal selection
- Maternal antibodies offer protection in first months
