Immunopathology Flashcards
What part of the immune system response involves T and B cells?
ADAPTIVE uses T and B cells
INNATE uses phaagocytes and NK cells
What are the major components of the innate immune system?
1) Pattern Recognition Receptors (PRR)
2) Antimicrobial peptides
3) Cells e.g. Macrophages, NK cells, Neutrophils
4) Complement components
5) Cytokines
What is the role of pattern recognition receptors (PRR)?
PRRs are part of the innate immune system. They are involved in activating inflammation and phagocytic activity when recognising pathogen associated molecular patterns (PAMPS).
What are fluid phase recognition molecules?
1) COLLECTINS are part of the C-TYPE LECTIN FAMILY
- Mannan-binding Lectin
- Surfactant Protein A & D
- They RECOGNISE microbial complex carbohydrates.
- Fluid phase recognition molecules are part of the PATHOGEN NEUTRALISATION pathway
- Recruite ADAPTIVE response
How is the classical pathway of the complement cascade initiated?
The formation of antigen-antibody complexes initiates the cascade
How is the MB-Lectin Pathway of the complement cascade activated?
The binding of Mannose-binding Lectin (MBL) to mannose on pathogen surface activates the complement cascade
How is the alternative pathway of the complement cascade activated?
Activated when C3b directly binds to a pathogen
What is the role of C3b in the complement pathway?
C3b binds to receptors on phagocytes and enchances phagocytosis.
C3b also gives rise to the terminal complement components (C5b, C6, C7, C8 and C9) which are membtane attack complexes that cause the lysis of pathogens.
what is the role of C3a and C5a in the complement cascade?
they are mediators of INFLAMMATION and PHAGOCYTE RECRUITMENT.
What is the role of macrophages in the innate immune system?
Phagocytosis
What is the role of plasmacytoid dendritic cells in the innate imune system?
produce interferon (IFN-) which has antitumour / antiviral activity.
What is the role of myeloid dendritic cells in the innate immune system?
Produce IL-2 and IL-10
What is the role of natural killer cells in the innate immune system?
Kill foreign (and host cells)
What is the role of NK-T cells in the innate immune system?
NK-T cells are lymphocytes with both T cell and NK surface markers.
Recognise intracellular bacteria
What is the role of neutrophils in the innate system?
Phagocytose and kill bacteria
What is the role of Eosinophils in the innate immune system?
Kill invading parasites
What is the role of Mast cell and basophils in the innate immune system?
Release TNF, IL-6 and IFN-
What is the role of epithelial cells in the innate immune system?
Produce anti-microbial peptides
What is the key feature of the adaptive immune response?
There is a unique antigen receptor found on each lymphocyte.
Infection causes CLONAL expansion of the lymohocyte
There is a high degree of specificity
What is the role of the primary lymphoid organs in the adaptive immune system?
The primary lymphoid organs are where lymphocyte development and selection occur.
B cells develop in the bone marrow.
T cells develop in the Thymus,
What are the secondary lymphoid organs of the adaptive immune system?
1) Spleen
2) Lymph nodes
3) mucosal surfaces
What is V (D) J antibody recombination?
- Alteration of the D and J segments of DNA allows for greater variation.
- occurs only in developing lymphocytes during the early stages of T and B cell maturation
What is the mechanism of antigen presentation?
1) Antigens are internalised
2) Broken into peptides
3) Peptides associate with class 2 molecules and presented on cell surface
4) Foreign peptides are recognised by T Helper cells.
5) T helper cells get activated and produce cytokines which stimulate B cells.
What are MHC (major histocompatibilty complex) / HLA (human leucocyte antigens) ?
cell surface proteins which bind to pathogenic peptides and display them on the surface of the cell for recognition by appropriate T cells,
What is the function of Class 1 and Class 2 MHC proteins?
1) T cells can only recognise antigens in association with MHC.
2) MHC 1 proteins present peptides to cytotoxic T cells.
3) MHC 2 proteins present peptides to helper T cells
What is the function of B lymphocytes?
B cells secrete antibodies (humoural activity)
What is the function of cytotoxic / Killer T cells?
they kill pathogens and provide cellular immunity
What is the function of Helper T lymphocytes?
Helper T cells secrete growth factors (cytokines) whcih control immune response
What type of immune cell is the target of HIV?
Helper T cells are the target of HIV
What are the different ways in which binding of antibodies to antigens inactivates antigens?
1) Neutralisation -
( blocks viral binding sites)
2) Agglutination of microbes (antibodies bind to antigens on the bacteria and cause them to aggregate and clump)
3) Precipiation of dissolved antigens (antibodies bind to antigens causing them to clump and precipitate)
Mechanisms 1, 2 and 3 make it easier for macrophages to phagocytose the pathogen.
4) Activation of the complement system leads to cell lysis
What is the mechanism by which T cells destroy infected cells?
1) cytotoxic T cell binds to the infected cell.
2) Perforin released by the killer T cell makes holes in the infected cell membrane.
3) An enzyme which causes apoptosis enters the cell and destroys
Describe the mechanism of T cell proliferation
An antigen presenting cell binds to the T cell this causes proliferation
What is the link between Immunosuppression and Immunodeficiency?
IMMUNOSUPPRESSION:
-turns off immune response, partially or fully, accidentally or on purpose.
-Immunosuppression can lead to immunodeficiency
IMMUNODEFICIENCY:
-Lack of an efficient immune system
What part of the immune system does Pneumococcus affect/
Pattern recognition receptors
What part of the immune system does HSV (herpes simplex virus) affect>
PRRs (pattern recognition receptors)
What part of the immune system does staphylococcus and aspergillus affect?
Phagocytic cells of the innate system (Macrophages and Neutrophils)
What part of the immune system does meningococcus affect?
Complement proteins
What is Hypersensitivity?
-Undesirable reactions produced by the normal immune system against non-harmful agents, in a pre-sensitzed host.
What are the 4 types of Hypersensitivity reactions?
1) IgE Mediated Reaction
2) Cytotoxic Reaction
3) Immune complex reaction
4) cell mediated reaction
What is the immunopathogenesis of Type 1 - Anaphylactic hypersensitivity reaction?
IgE Ab mediated mast cell and basinophil degranulation releases inflammatory mediators e.g. Histamine
What result of Mast cell activation in IgE Hypersensitivity?
Mast cell activation :
1) Degranulation
2) Synthesis of Lipid Mediators
What is the effect of histamine, Kallikrein ?
1) Histamine :
- Smooth muscle contraction and increase in vascular permeability
2) Kallikrein:
- activated bradykinin (similar to histamine)
Give examples of allergic disease?
1) Asthma
2) Rhinitis
3) Dermatitis
4) Food Allergy
What is the mechanism of Type 2 Hypersensitivity?
CYTOTOXIC Reaction
Antibody binds to target antigen causes:
- complement cascade»_space;> cell lysis
- opsonisation, phagocytosis and destruction
What type of immunoglobulin is associated with type 2 hypersensitivity?
IgM or IgG
What is the mechanism of Type 3 hypersensitivity?
Immune complex reaction :
-complement activation»_space;> phagocytosis»_space;>tissue damage
Describe the mechanism of Type 4 Hypersensitivity?
T cell mediated . -CD4 T cell recognises antigen in association with MHC class 2 protein on APCs (macrophages)
-These CD4 T cells release cytokines which recruite macrophages which cause tissue damage.
CD8 T cells destroy the target cells
the activated
What are granulomas?
Granulomas are collections of inflammatory cells in tissues.
cells include:
- macrophages
- giant cells
- lymphocytes
give examples of granulomatous diseases
- TB
- Leprosy
- Crohn’s
