Pathology and host defence Flashcards
What do the gamma delta T cell subsets display in host defence and what does this allow?
Functional heterogenesis, so they can play a role in:
- Immunosurveillance
- Gingival homeostasis.
What is the role of rete pegs on the epithelium of gingiva?
They increase the surface area for contact between epithelium and connective tissue which in turn contribrutes to mechanical stability.
What does the space between the junctional epithelium and the tooth contain?
- GCF which contains immuniglobulins and neutrophils.
- IgM or IgG in GCF can activate complement and being about bacterial cell death. They can promote phagocytosis directly or through complement activation.
What is the epithelium that lines the gingival sulcus called?
The sulcular epithelium
It is apically bounded by the junctional epithelium and meets the epithelium of the oral cavity at the height of the free gingival margin. The sulcular epithelium is nonkeratinized.
What is the role of sIgA on the gingival mucosal surfaces?
It prevents bacterial adherence and neutralises bacterial toxins.
What are the 4 stages of lesions that lead to periodontitis and what is seen in each stage?
- Initial lesion (24-48 hours)
Localised to gingival sulcus and subjacent periodontal tissue. There is some perivascular loss of collagen within the gingival connective tissue.
- Early lesion (4-7 days) (gingivitis)
Localised proliferation of junctional epithelium and sulcular epithelium. Some loss of collagen subjacent to the junctional and sulcular epithelium.
- Established lesion (2-3 weeks)
Proliferation of junctional epithelium and sulcular epithelium, further loss of collagen within the gingiva, but no LOA (loss of attachment)
- Advanced lesion
Pocket formation, LOA, collagen destruction within the periodontal ligament and bone loss. An imbalance in the host-microbial interaction heralds the transition from a successful defense to a destructive pathological reaction. There is also a reparative fibrotic response, which becomes more evident with time.
What is complement and what does it do?
- Is a group of 20 proteins in the process.
- The protein is broken down into a big bit - membrane attack complex (MAC) which kills bacteria by punching cationic pores into the cell membrane.
- And a small bit which has additional biological function that promotes the inflammatory response
What are the 3 different ways complement can be activated?
- Classical pathway
Antigen antibody complexes (C1Q, C1r, C1s, C4, C2) → bind to C3 convertase.
- Lectin pathway
Mannose-binding lectin or ficolin bind carbohydrate on pathogen surfaces (MBL/ficolin, MASP-2, C4, C2) → binds to C3 convertase.
- Alternative pathway
Pathogen surfaces (C3, B, D) → bind to C3 convertase.
What are the roles of complement C3a and C5a after the C3 convertase stage?
They are peptide mediators of inflammation, phagocyte recruitment.
What are the roles of complement C3b after the C3 convertase stage?
- They bind to complement receptors on phagocytes
- Cause opsonisation of pathogens
- Removal of immune complexes
What are the roles of complement C5b, C6, C7, C8, C9 after C3b complement is activated?
- They form a membrane-attack complex.
- Causing the lysis of certain pathogens and cells.
What is the function of neutrophils?
Phagocytosis and activation of bactericidal mechanisms.
What are the stages of neutrophils migrating into cells?
- Rolling adhesion with the aid of E-selectin on the surface and the s-Lex receptor on the neutrophil.
- Tight binding via ICAM-1 receptor on the surface of the cell and the LFA-1 receptor on the neutrophil.
- Diapedsis- neutrophil goes into cell.
- Migration- in cell towards chemokine CXCL8 (IL-8) (neutrophil has CXCL8R receptor)
Give 2 roles of a macrophage.
- Phagocytosis and activation of bactercidal mechanisms.
- Antigen presentation.
As macrophages are capable of presenting antigens to T cells what does this promote?
Adaptive immune responses.
In what cells are Toll-like receptors (TLRs) present in?
- Immune cells
- Epithelial cells
- PMNs
- Macrophages
- Dendritic cells
What TLRs recogniase gram-negative organisms?
TLR4 and TLR5.
What TLRs recogniase gram-positive organisms?
TLR2 and TLR5 gram-positive organism
Which TLRs are located on the cell surfaces and which ones are found intracellular?
- TLR-6, TLR-2, TLR-5, TLR-4. cell surface
- TLR-3, TLR-7, TLR-9
What is the main role of cytokines?
Communication between immune cells and non-immune cells.
what th elocal effects of cytokines?
look at notes
what the systemic effects of cytokines?
look at notes
Give 2 cells present in humoral responses.
- B cells
- Plasma cells and antibodies.
Give 3 ways antibodies assist in protecting the host.
- Neutralisation - By receptors binding to bacterial toxins. Leads to ingestion by macrophage.
- Opsonisation - By macrophages binding to bacteria in extracellular space.
Leads to ingestion by macrophage.
- Complement activation -
By bacteria in plasma cells.
Leads to lysis and ingestion.
