Defensive Barriers

Defensive Barriers

1. routes of infection

   • Horizontal transmission
     • direct contact
     • aerosol
     • oroa-faecal
     • vector borne
   • vertical transmission
     • direct contact

2. Defensive barriers

   • physically barriers
     • skin
   • physiological barriers
     • mucous membrane
   • biochemical barriers
     • gastric acid
   • chemical barriers
     • lysozyme
   • cellular
     • macrophages

3. Commensal flora: 'friendly bacteria"

   • produce microbial molecules
     • prevent pathogenic organisms infecting

4. physical barriers

   • keratinocytes replicate to generate stratified squamous keratinised epithelium
   • melanocytes protect from UV damage

5. immune

   • Langerhanns cells
     • immune sentials
     • pathogens into lymphatic system to lymph node

6. Respiratory System

   • Mucous
     • water and electrocytes, glycoproteins and lipids
     • antimicrobial compounds
       • transferrrins
       • lactoferrrin
       • lysozyme
     • antibodies
     • antioxidants
       • superoxide dismustase
       • catalase
       • glutathione peroxidase
     • cilia beat mucus with trapped foreign objects up and out
   • respiratory pathology
     • impairment of mucociliary escalatory predisposes lung to pathology
       • virus infection
       • trauma
       • toxins
     • bacterial bronchopneumonia is often a secondary infection
   • alveolar macrophages
     • main line of defence against inhaled microbial pathogens
     • short lifespan in alveoli
     • derived from blood monocytes and interstitial macrophages

7. Sebaceous glands and sebum

   • water repellent
   • contains fatty acids (ph 5.5)
   • antimicrobial components

8. AMPS: beta- defensins

   • small cationic peptides
   • broad spectrum anti-microbial properties
   • disruption of microbial membranes and/or interference with intercellular functions
   • human: HBD1 constitutive expressed keratinocytes, HBD2-4 inducible in keratinocytes in response to infection
   • dog: 3 beta-defesin genes unidentified to date
   • keratinocytes trigger inflammation
     • produce cytokines (immunological hormones)
     • produce chemokine (cell migration factors

9. Alimentary tract

   • oral cavity and oesophagus
     • protection against trauma and infectious agents
     • biochemical barrier is lysosome in saliva
     • stratified squamous epithelium
   • stomach
     • sterilisation and digestion of food
     • Hcl
     • pepsin
     • mucous
     • regulatory peptide
   • small intestines
     • cryptidins
     • toxic to bacteria
     • synthesised by panted cells present in intestinal crypts
   • GIT
     • Lymphoid tissue-factor where you make immune responses
     • specified mucosal protective antibody (IgA)