Having An Operation CPC

2.2.07

Pre-op work-up
• Haematology.
• Biochemistry.
• CXR/ECG.
• Special cases.
-Drug history, especially steroids.
-DM.

Anaemia
• Haemorrhage.
• Iron deficiency.
• Megaloblastic (including pernicious anaemia).

Blood transfusion
• When to give it.
• Group and save.
• Emergency situation.
• Cross-match.
• Risks.
-Reactions.
-Infections.
• Auto-transfusion.

Wound infections
• Cellulitis (Strep.)
• Abscess (Staph.)
• Commonest organisms.

Bacterial damage
• Virulence increased with population density.
-Adherence.

Adherence
• Adhesins.
-Fimbriae/pili on Gram negative bacteria.

Invasion
• M. tuberculosis.
-Opsonised with C3.
-Invades macrophages via C36 receptor.
-Phagosome/lysosome fusion blocked.
• Gram-negative bacteria.
-Inject "transmitter" proteins into cell that rearrange structure and facilitate entry.

Toxins
• Exotoxins.
-Enzymes.
§Protease.
§Hyaluronidase.
§Coagulase.
-Signal blockers.
§Receptor binding part + enzyme.
-Neurotoxins.
§Botulinum, tetanus.
-Superantigens.
§Toxic shock syndrome.
~Stimulate many T cells → cytokines.
• Endotoxins.
-Lipopolysaccharides.
§Constant part and variable ("O") part (O157).
§Small doses enhance immune response.
§Large doses overwhelm it e.g. sepsis.
~DIC.
~ARDS.
~Cytokine release (IL-1, IL-2, TNF-α).

Lung infections
• Pneumonia.
• Organisms.
-Pneumococcus.
-Haemophilus.
-Klebsiella.
-Legionella.
-Opportunists.
-Fungi.
-Viral.

Wound Healing

2.2.07

Terms
• Resolution e.g. lobar pneumonia.
• Repair.
• Regeneration.
• Organisation.
• Replacement.

Regeneration
• Labile cells.
-Epithelia, blood cells.
• Stable cells.
-Organs with "no" stem cells e.g. liver.
• Permanent cells.
-Neurones in CNS.
-Muscle (skeletal and cardiac).
• Role of stem cells in regeneration.

Regeneration of stable cells
• Mitogenic signals.
-Autocrine.
-Paracrine.
-Endocrine.
• Receptors.
• Signal transduction.
• DNA-binding proteins.
• Framework required.

Organisation
• Exudate.
• Fibroblasts and blood vessels.
• Collagenous scar.
• E.g.
-Peritoneal adhesions.
-Pericarditis.
-Pulmonary fibrosis.

Wound healing
• Primary intention.
-Clean surgical wound firmly apposed.
• Secondary intention.
-Large, denuded wound e.g. abrasion, burn.

Events in wound
• Haemorrhage → clotting.
-Platelets.
-Fibrin(ogen) and fibronectin.
• Epidermis.
-Cells migrate over wound.
§Marginal keratinocytes interact with fibronectin.
§Cells proliferate (start 12 hours after wounding).

Events in wound - dermis
• Neutrophils → wound (12-24 hours).
• Macrophages → wound (24 hours+).
-Demolition.
-Angiogenesis.
§Vascular buds; leaky, fragile capillaries.
§Granulation tissue.
-Stimulation of fibroblasts.
§VEGF increases permeability and leakage.
§Macrophages produce PDGF, TGF-β and FGF.
-Collagen maturation.

Growth factors
• EGF (epidermal).
-Also stimulates mesenchyme.
-Mouth and GIT, but not skin wounds.
• PDGF (platelet-derived).
-Mitogenic, chemoattractant (chemotaxis).
• FGF (basic fibroblast).
-Angiogenesis.
-Cell migration.
-Haemopoiesis.
-Muscle and lung maturation.
• VEGF (vascular endothelial).
-Vasculogenesis in embryo.
-Angiogenesis (tumours, healing).
-Varieties: -C acts on lymphatics.
• TGF-α (transforming).
-Homology to EGF - found in wounds.
• TGF-β.

Cytokines
• Produced by inflammatory cells.
-IL-1.
§Stimulates fibroblasts to divide, synthesise collagen and also produce collagenase.
-TNF-α.
§Tumour cell killing.
§Wasting.
§Inflammatory diseases/conditions.
§Stimulates new blood vessels.

Collagen and extracellular matrix
• ECM.
-Collagens and elastins.
-Adhesives: fibronectin, laminin.
-Proteoglycans and hyeluronan.
• Collagen.
-14 types.
§Types 1-3 fibrillar.
§Type 4 in basement membrane.

Wound strength regained
• 10% at 1 week (stitches out).
• Increases to 70% by 5 weeks and plateaus at ~ 80%.
• GIT anastomosis 90% by 8 days.

Large wounds
• Secondary intention.
-More granulation tissue.
-Wound contraction.
§Myofibroblast (contains actin, but no myosin).
§Fibronectin molecules bridge myofibroblasts and collagen fibres.

Factors limiting wound healing
• Systemic.
-Lack of:
§Protein.
§Vitamins (A, C).
§Zinc.
-Steroids.
-Age (?)
-Diabetes.
• Local.
-Lack of immobilisation.
-Foreign body/infection.
-Blood supply (including venous drainage) e.g. leg ulcers.
-Poor oxygenation.
• Complication: keloid scar.

Healing of bone
• Fracture → haemorrhage.
-Inflammation.
-Necrosis locally.
-Granulation tissue.
• Provisional callus.
-Woven bone with cartilage islands.
• External callus.
• Remodelling.
-Possible sources of failure.

Module 2.09

Having An Operation.
29.1.07 - 9.2.07.

The Immunology Of Rheumatoid Arthritis

22.1.07

What is RA?
• Chronic and inflammatory disease of some joints and often other tissues.
• Mechanism(s) leading to activation of immune system unknown - AUTOIMMUNE DISEASE.

Conventional view of autoimmune disease
• Autoimmunity: abnormal immune response that destroys otherwise normal tissue.
• Abnormal activation of offending immune cells (very often CD4+ T lymphocytes).

Function of immune system
• Recognise changes (due to infections/malignant transformation) by constantly monitoring all cells in body.
• When change is detected, attract the necessary responding cells into close vicinity.
• Eliminate changed cells and remove the debris.
• Terminate the response (by killing most responding cells).
• Provide some memory in case same change occurs again.

Island empire analogy
• Imagine body = island.
• Immune system acts as border patrol, police and army.
• Role:
-Not to let anybody in.
-Eliminate all defectors.

Divisions of law enforcement
Pest control officers (granulocytes)
• Lots, everywhere.
• Short-lived.

Community patrol officers: professional antigen-presenting cells, dendritic cells
• Present everywhere, but numbers higher at sites where invasion from outside likely e.g. skin, gut, liver.
• Get despatched to area where they remain stationed for long time.
• Listen, but do not talk.
• Good at picking up antigens, but not presenting.
• Once older. Go back to base to report.

Commanding officers: CD4+ T"helper" lymphocytes
• Lots (CD4:CD8 = 2:1).
• Have been drilled in thymus: if community patrol officer reports "A," give specific order "B."
• No space for individual decision-making.
• TCR expression establishes antigen-specificity - cytokine response profile predetermined.
• Bit of confusion in differences in cytokine production following same antigenic stimulus, TH1 vs TH2 cells.

Cytotoxic (CD8+) lymphocytes: foot soldiers of the empire
• Have been trained at same camp (thymus) as commanding officers.
• Can see enemy (have TCR for antigen recognition).

Chemical response team: B lymphocytes (and complement)
• Relatively few.
• While foot soldiers walk up to enemy and kill it in close quarters, chemical response team concocts poison.

Monocytes/macrophages
• Bit of Jack-of-all-trades.
• Eat pests, just like pest control (direct Phagocytosis).
• Eat unwanted citizens (ADCC, apoptotic cells).

What is autoimmunity?
• Revolt (citizens fail to behave and they get punished for it)?
• Reconnaissance failure (community officers misinform commanders)?
• Have commanders gone beserk (abnormal T cell activation)?
• Is it something else?

Evidence for innocence of synovial cells
• Transplanted arthritic synovial tissue in immunocompromised host: disease stays active (for how long, though?)
• If you eliminate inflammatory cells: synovium returns to normal.
• Animal experiments: can transfer inflammatory arthritis.

Prosecution's view
• Take immunocompromised host.
• Transplant normal synovium at one site, arthritic synovium at another distinct site, and observe.
• Aggressive, proliferating synovial cells (not lymphocytes) migrate to healthy synovium.
• These cells behave like metastatic tumours (in inflammatory arthritis, same enzymatic system is active that facilitates metastases formation in cancer).

Further evidence for guilt of synovial cells
• Establish monolayer of cells from synovial fibroblasts.
• Place on top of patient's own lymphocytes.
• Inflammatory foci will develop in well-defined areas.
• Mark these areas.
• Increasing evidence that synovial cells show significant changes in RA.
• However, whether defects described to date cause initiation of RA remains to be seen.

Principals of DC antigen presentation
• Origins of DC:
-Monocytic.
-Myeloid.
-Plasmocytoid.
• Common feature: maturation.
-Immature cells pick up antigens.
-mature cells present them.
• Question: when is DC signal activating and when is it tolerogenic?

Extended functionality of B cells
• "Chemical response team" view simplistic: these guys undergo significant maturation during life span and almost think sometimes…
• Resting/immature B cells have antigen-specific receptors, but are very inactive.
• When activated by commanding officers (in right cytokine environment provided by CD4+ T cells), B lymphocytes:
-"Fine tune" antigen receptors (somatic hypermutation).
-Start expressing.

Story of three mice - does this work in humans?
• In some RA patients, elimination of active mature B cells with anti-CD20 antibody leads to long-lasting disease remission.
• Unfortunately, CD20 not unique B cell marker.
• Some T cells and dendritic cells also express it.

Role of commanding officers
• A lot around joints (but not quite as many as some T cell immunologists would like you to believe).
• Do look nasty…
• …And remember animal experiements.

Why CD4+ T cells could be less important than originally thought
• Almost all of these cells of memory phenotype.
• Would be recruited (rather than non-specifically) to any inflammation site, just in case you need them.
• Do not proliferate much, do not produce IL-2 much - if anything, are a bit depressed.
• Eliminating them does not bring spectacular success in therapy.

Question
• Why do these memory T cells end up in the joints?
• Answer: don't know.
• If we did, could prevent and cure RA.
• It is something that is very difficult to study.

Is RA result of abnormal T cell regulation?
• In healthy individuals, there are a number of safety mechanisms that switch off ongoing immune response.
• Many of these seem either defective/inefficient in RA.

Regulatory pathways
• Activation-induced cell death.
• CD4+, CD25+ regulatory T cells.
-Tolerise activated T cells via direct cells contact.
• Type II regulatory T cells.
-Produce tolerogenic cytokines.
• NKT cells (CD1d restricted, Vα24+ T cells).
-Induce tolerance via IL-4, IL-12 production.
-Recent evidence indicates interaction with DCs.
• NK cells (CD158-, CD94bright NK cells).
-Kill immature DCs affecting antigen presentation.

Final word of cytokines
• "Words" by which members of immune system communicate with each other.
• Language not that complex (compared to human verbal communication).
• Some of these "words used very often - some cytokines involved in multiple, vital regulatory pathways.

Autoimmune Disease

19.1.07

Autoimmunity
• Central tolerance.
-Thymus (T-cells).
-Bone marrow (B-cells).
-Clonal deletion of self-reacting cells.
-Come are missed - present in normal health.
• Peripheral tolerance.
-Regulatory CD4+ T-cells [CD=cluster designation - apply to some membrane antigens - ~200, but low numbers tend to be discovered first.]
-Anergy of lymphocytes (irreversible).
-Clonal deletion (activation - induced cell death).
-Antigen hiding.

T-regulator cells
• CD4+, CD25+, foxp3++.
• Suppress autoreactive T-helpers permanently.
• Outcompete other T-cells for APC binding.
• Inactivates antigen-presenting cell (prevents stimulation of other T-cells).
• Binds onto APC adjacent to T-cell and inhibits it directly.

Autoimmunity
• Loss of tolerance.
-Genetic factors (HLA, AIRE, Fas, CTLA-4).
-Infection.
§General factors.
~Cytokines.
~Release of damaged proteins.
~Molecular mimicry.
§Homologous sequences e.g. strep.
-Hidden sites: special effects in eye, brain, testes.
• Generalised.
-Connective tissue disorders.
• Single/restricted organ damage.
-Hashimoto's.
-Pernicious anaemia.
-Goodpasture's.
-etc.

Connective tissue disorders
• Rheumatoid arthritis.
• Systemic lupus erythematosus (SLE).
• Scleroderma.
• Etc.

Rheumatoid arthritis
Overview
• Systemic disease, mainly involving joints, but also:
-Blood vessels.
-Skin.
-Muscles.
-Lungs.
-Heart.
• Incidence ~1%, mainly F 40-70 (F:M ratio = 3:1).

Joints
• Stages.
-Villous synovitis.
-Vascularises.
-Fibrinous exudates (rice bodies and pmn).
-Osteoclastic activity increased.
§Erosions, cysts, juxta-articular osteoporosis.
-Pannus formation.
§Synovium and granulation tissue.
§Covers and erodes cartilage.
§Bridging and anklosis.

Other sites
• Skin.
-Rheumatoid nodules (elbow, head, back).
§Necrosis and palisaded macrophages.
• Blood vessels.
-Vasculitis.
§Neuropathy and gangrene.

Pathogenesis
• Immunology: excessive CD4+ cells, but unknown trigger (??Proteus).
• Twin concordance - genetic, but not simples.
• No clear HLA linkage.
• Immune complex deposition.
• Excessive TNF and IL-1 from macrophages and synovial cells.

Clinical
• Onset.
-Often slow, with:
§Malaise.
§Fatigue.
§Generalised pain in limbs.
-Small joints involved first.
§Hands and feet, tends to progress centrally.
• Hot, swollen joints.
-Develop deformities later.
• Painful after resting.
• Remitting, relapsing disease.
-Baker's cyst.
• X-ray findings.
-Erosions, narrowed joint, osteoporosis.
• Tests - none very specific/sensitive.
-Rheumatoid factor.
§IgM anti IgG-Fc.
-ESR.
• Diagnosis in presence of more than three of the following:
-Morning stiffness.
-More than two arthritic joint groups.
-Hands involved.
-Symmetrical involvement.
-X-ray changes.
-Rheumatoid nodules.
-Rheumatoid factor.

SLE
• Most protean (multisystem) of them all.
• Chronic remitting relapsing disease, often febrile, characterised by injury to skin, joints, kidney, serosal membranes.
• Incidence: 1/2500, F:M ratio = 9:1, age 10-30 commonest (1:700 young women).

Clinical
• May start acutely.
-Sudden onset.
-High fever.
• Red raised (malar) rash frequently present.
• Frequent, recurrent pleurisy.

Genetics
• Twins (20% vs 2%).
• HLA (A1, A8, DR-2, DR-3).
• Inherited complement deficiency (C1q, C2, C4 in 6%).
• C1q needed to clear apoptotic cells.

Environmental
• Drugs.
-Penicillamine.
-Procainamide.
-Hydrallazine.
• UV light.
-?immunosuppressive role.

Hormonal
• Sex hormones.
-Much commoner in females.
-SLE may flare during:
§Pregnancy.
§Menstruation.

Serology
• Antinuclear antibodies:
-D-DNA.
-S-DNA.
-RNA.
-RNA protein.
-Histone.
-Nucleoli.
• Anti-blood cell antibodies: immune complexes.
• Patients affected in %:
-Fever 84%.
-Skin rash 72%.
-Renal 60%.
-Pleural 50%.
-Heart 50%.
-CNS 25%.
• Remitting fever with crises etc.
• Criteria:
-Renal damage.
-CNS signs (seizures, psychosis etc.)
-Blood cytopenias.
-Autoantibodies (including antiphospholipid).

Anti-phospholipid antibodies
• Actually directed against plasma proteins complexed to somewhere else.
• May give false and WR (cardiolipin).
• Lupus anticoagulant in vitro, but…
• Procoagulant in vivo.
-DVT.
-Repeated miscarriage.
-Cerebral ischaemia.

Scleroderma
• Main characteristic: excessive fibrosis throughout body.
• Skin, GIT, kidney, heart, muscle, lungs.
• F:M ratio = 2-5:1.
• Immunology: activated CD4+ cells in skin of many patients.
• Characteristic antibodies: Scl 70, anti-centromere.
• Hypotheses:
1. Autoimmune trigger for collagen synthesis.
2. Abnormal collagen metabolism.
3. Microvascular abnormality.
• Clinical.
-Thickening of hand ± Raynaud's.
-Articular pain.
-Dysphagia.
-Pain.
-Obstruction.
-Malabsorption.
-Renal damage.
-Hypertension.
-Diffuse fibrosis.
• "CREST": benign variant: calcinosis, Raynaud's, oesophageal fibrosis, sclerodactyly.

Polymyositis/dermatomyositis
• Myopathy and weakness due to degenration of groups of muscle fibre, with inflammation.
• Types.
-Typical adult myositis, dermatomyositis.
-Malignant associated (12%).
-Childhood.
-Associated with other connective tissue disease.
• Immunology:
-Some antinuclear antibody, possibly specific.
-Childhood type features immune complexes.
• Clinical.
-Initially arm, then proximal leg.
-Later, extends to limb girdles, neck, pharynx, intercostals and diaphragm.
-Initial oedema, then atrophy.

Sjögren's disease
• Primary: sicca syndrome.
• Secondary: with other autoimmune diseases.
• Decrease in salivary and lachrymal secretions due to lymphocytic infiltrate and fibrosis.
• Immunology:
-Some B-cells.
-75% have RF.
-65% have antinuclear factor.
-LE test positive in 25%.
-Antibody to duct cells, smooth muscle mitochondria, GPC, thyroid.
-SS-A and SS-B antibodies.
-If RA also present, RANA found.
• Clinical.
-Corneal ulceration.
-Oral fissuring and ulceration.
-Dry nose.
-Possible bronchial involvement.
-25% cases involve extraglandular tissues.