Phase 1


Innate Immunity

Complement pathway

1. Classical: Antigen-antibody complex C1qrs, C4, C2

2. MB-Lectin: Mannose on pathogen MBL, MASP, C4, C2

3. Alternative: Pathogen C3, B, D 

C3 convertase: C4a, C3a, C5a: Recruitment phagocytosis

C3b: Opsonisation
C5b, C6,7,8,9: Lysis 

Gram negative: Lipopolysaccharide (2 phospholipid membrane, inner peptidoglycan)
Gram positive: Lipoteichoic acid (outer peptidoglycan and inner cytoplasmic membrane)

TLR 1/2/6: Peptidoglycan, Lipoprotein, Lipoarabinomanannan (mycobacteria), GPI (T.cruzi), Zymosan (yeast)
TLR 3: dsRNA (viral)
TLR 4: LPS (Gram negative)
TLR 5: Flagellin
TLR 9: Unmethylated CpG DNA

1 of 18

Innate Immunity

NOD 1: y-glutamyl diaminopimelic acid (PGN negative)
NOD 2: muramyl dipeptide (PGN)

Neutrophils: O2 burst (reduced by NADPH oxidase to form hydroxyl radicals): H2O2 + Cl. = OCl. + H2O 
OCl.+H2O= O2+Cl.+H2O/ 2O2. + 2H+=H2O2 + O2 SOD/ H2O2= H2O + O2  

Macrophages: INFy+TNFa= O2+ Arg= NO synthetase= NO + Citrulline (+ Tetrahydrobiopterin)

IL-1/6: Inflammation, fever

TNFa: Fever, macrophage

IL-12: CD4 T cell differentiation

IL-8: macrophage, endothelial cells

MCP: monocyte chemotactic protein  

IFNa/IFNb: Natural Killer: TNFa/IL-12--> IFNy--> Macrophages and /CD4+ Th1 cells 

2 of 18

Adaptive Immunity

Ig heavy chain gene rearrangement: VDJ - Also T cell Receptor beta and delta

Ig light chain gene arrangement: VJ - Also T cell Receptor alpha and gamma

Junctional Region Diversity: TdT adding random nucleotides

B cell this happens- Bone marrow

T cells- Thymus

B cells ONLY

Hypermutation and affinity maturation- germinal centre of B cell folicles (tonsil, spleen) dark zone

Class switching

3 of 18

Adaptive Immunity

IgG (1/2 etc) In blood after class switching- opsonisation- antibody-dependent cellular cytotoxicity

IgE Mast cell and degranulation/ parasitic 

IgA Mucosal antibody (B cells at surfaces and in breast milk) - form protective dimer

IgM Pentamers (too large to pass into tissues and cross placenta)

IgD Naive B cells (membrane-bound)

4 of 18

T cells effector and function

MHC 1: a1/a2/a3/b2m - endogenously expressed on nucleated cells CD8+

MHC 2: a1/a1/b1/b2 - aB hetrodimer expressed on antigen presenting cells CD4+

Class 2, 3, 1 on short arm of chromosome 6 in co-dominant manner 

T cell receptor: a (Va/Ja/Ca) b (Vb/Db/Jb/Cb)

4.5 x 10^9 TCR possible 

Costimulation- CD28/86 

5 of 18

T cells effector and function


IL-12--> Th1--> IFNy/IL-2 

Intracellular pathogens (Listeria, TB, Leprosy)

IFNy--> macrophages

IL-2/IFNy--> CD8+ T cell


IL-4--> Th2--> IL4/5/13/2

Extracellular parasites (Schistosoma, Tricinella)

Division, Class switching, Affinity maturation, differentiation


TGFb/IL-6--> Th17--> IL-17/22

Extracellular bacteria (Klebsiella pneumoniae, candida albicans) 

Neutrophil, epithelium/fibroblasts

6 of 18

T cells effector and function


TGF-b + IL-2--> Treg--> TGFb/ IL-10 

Suppress activity of APC, proliferation of responder, cytokines, antibody, NKT/NK

nReg: naturally occurring (in thymus)- self antigens/ autoimmunity
Lack of: IPEX  

aTreg: adaptive (periphery)- autoimmunity

T cells derive from bone marrow precursors and develop in thymus

Thymic education: Positive selection for MHC in thymic cortex

Negative selection to eliminate high affinity self-reactive T cells in thymic medullary epithelial cells

Activation of naive lymphocytes occurs in lymphoid organs 

7 of 18

Immunological Memory

Bone marrow--> Tm --> High frequency, avidity and immediate effector function

LN--> Plasma cell --> Secrete high affinity ab, live for years

Spleen--> Bm --> High frequency, develop into plasma cells 

8 of 18

Immunological challenges

Type 1 Hypersensitivity/Allergy

Atopy- inherited predisposition 

Pollen--> APC MHC 2--> CD4+ T cell--> IL-4--> Th2--> IL4,5,13--> B lymphocyte--> P--> IgE--> Mast cell

Asthma, perennial rhinitis, ecxema, anaphylaxis


Grave's Thyroiditis- Th2--> B cell --> P--> TRAb autoantibodies --> TSH-R/ -->EXCESS THYROID HORMONES

Diabetes Type 1- Islet cell autoantibodies: Insulin, GAD65, IA-2, ZnT8

APC/HLA--> T --> CD8 Tc --> Kill B cell 
Th1/17 (IFNy,TNFa/IL-17)--> B lymphocyte--> P --> Autoantibodies + Macrophage  

9 of 18


Absent thymus- severely reduced T cell number and function- DiGeorge

Defective T cell activation- Reduced T cell- CD3y chain mutation

Defective B cell maturation - Hyper IgM syndrome

Defective APC/T cell interaction- Reduced granuloma and IFNy receptor deficiency

Neutrophil failure- chronic granulomatous diasease 


10 of 18


Animal and plant cells: Cell membrane, DNA & RNA, 80S (or 70S) Ribosomes 10-100um

Bacteria: Cell wall and membrane, DNA & RNA, 70S Ribosomes 0.3-3um

Viruses: DNA or RNA, Nucleocaspid 20-200nm 

Gram positive: blue/purple low lipid exotoxins 

Gram negative: red high lipid endotoxin, don't survive drying

11 of 18

Gram Positive Bacteria

Gram Positive Cocci: 

Staphylococci (Clusters)

Staph. aureus: PVL, aby toxins, Enterotoxins A-F (E= TSST1), coagulase positive, protein A 


Streptococci (Pairs/Chains)

a Haemolytic: Strep. pneumoniae 

b Haemolytic: A (pyogenes) Streptolysins, kinase, hyaluronidase B C 

Cellulitis, pharyngitis and rheumatic fever (pyogenes)

Non-haemolytic: enterococci, anaerobes 

Gram Positive Rods: 

Anthrax, Tetanus, Botulinum (Spores)

Diphteria, Nocardia (No Spores)

12 of 18

Gram Negative Bacteria

Gram negative cocci

Gonorrhoea, meninogoccocal meningitis 

Gram negative rods

E. Coli UTI/peritoneum, Klebsiella, Proteus, Pseudomonas (aeruginosa) Contact lenses, infection leukaemics, ITU- enzymes, elastase, endotoxin 

Shigella, Salmonella, Campylobacter, Brucella, Legionella, Anaerobes, Haemophilus 


Mould: Aspergilus, Mucor


Dimorphic Fungi: Histoplasma


Protoza: malaria, amoeba 

Helminth- Nematode- roundworm
Trematode- flukes  

13 of 18

Fever and Sepsis


1. TNFa/IL-1/IL-6 increase in blood from macraphages, monocytes and B cells

2. Hypothalmic thermoregulatory centre PGE2 - IgG 

3. Elevation of set point 


Exotoxin: TSST1 SPEA/C
Endotoxins: LPS  


Infection with unusual pathogen: Pneumocystitis, mycobacteria

Reactivation or severe infection: Toxoplasma, PCP, CMV 

14 of 18

Viral Infections

DNA Virus: Icosahedral, Spherical

Parvovirus: parvovirus B19 **
Papovirus: papillomaviruses ds
Hepadnaviridae: hepatitis B ds envelope 
Adenoviridae: resp tract, eye ds
Herpesviridae: herpes simplex, VZV, CMV, EBV ds 

RNA Virus: 

Picornaviridae:spherical, icosahedral **+ -rhinovirus, polio
Orthomyxoviridae: spherical/filamentous and helical **- envelope - influenza A/B
Paramyxoviridae:spherical/filamentous and helical  **- envelope - mump, measle
Retroviridae: spherical **+ envelope- HIV1/2

15 of 18

Viral Infections

HIV 1: CD4/ CXCR4 T cells/ CCR5 macrophages 

Rabies: ACh

EBV: C3d receptor B cells

Vaccinia: EGFR

Reovirus Type 3: B adrenergic hormone receptor

Rhinovirus: Glycophorin A molecule

Influenza: Sialic acid on glycoproteins (glycophorin A molecule)

Encephalomyocarditis: Glycophorin A molecule  

16 of 18


Exudate: Inflammatory extravascular fluid with high protein conc. and much cellular debri S.G>1020

Transudate: Ultrafiltrate of low protein (albumin) S.G. < 1012

Pus: Exudate in Neutrophils and parenchymal cell debri

Chemotaxis Neutrophils-->

  • Bacterial products
  • c5a
  • LB4 (arachiodonic metabolism in lipoxygenase pathway)

Acute suppurative inflammation (pus) appendicitis

Acute fibrinous inflammation pneumonia

Acute membranous inflammation psudomembranous colitis 

17 of 18

Chronic Inflammation

1. Infiltration by macrophages, lymphocytes and plasma cells

2. Proliferation of fibroblasts and small blood vessels 

3. Granuloma (lymphocytes and macrophages) 

Pulmonary TB 

18 of 18


No comments have yet been made

Similar Medicine resources:

See all Medicine resources »See all Immunology and Microbiology (Theme 7) resources »