What is humoral immune responses to infections as a broad definition?
Innate and adaptive immune responses mediated by soluble (cell-free) immune system
Fill in the blank:
Bacteria induce ____ to produce ____, which acts on ____ to induce synthesis of ____-____ proteins.
Bacteria induce macrophages to produce IL-6, which acts on hepatocytes to induce synthesis of acute-phase proteins.
Does C-reactive protein bind to phosphocholine on bacterial surfaces? If yes, what does CRP act as?
Yes, it acts as an opsonin and complement activator.
MBL (mannose-binding lectin) binds to carbohydrates on bacterial surfaces. True or false?
True
What are the 4 ways in which a microbe can evade complement activity?
- Inhibit alternative pathway of complement activation
- Inactivate complement components
- Bind plasma proteins that negatively regulate complement activity
- Impair opsonisation and phagocytosis
What is the structure of an immunoglobulin?
It has an antigen binding domain, a complement binding site and placental transfer site - the last 2 binds to Fc receptors
What is the relationship between hemagglutination-inhibiting antibodies and protection against influenza?
Higher hemagglutination-inhibiting antibodies numbers in the body increases the level of protection against influenza.
How does opsonisation enhance phagocytosis?
The microbe is coated with opsonising antibodies. This can bind to opsonin receptors on the phagocyte, with co-stimulation of PRRs (pattern recognition receptors) of the phagocyte by the microbe leads to enhancement of lysosomal degradation of the microbe.
Are elderly adults with lower opsonophagocytic antibody more susceptible to pneumococcal disease?
Yes - low opsonophagocytic antibodies are strongly correlated with low IgG antibody activity
What are four mechanisms by which the complement pathway controls infection?
- Activates MAC to lyse bacteria
- Opsonizes pathogens
- Actives inflammatory response by triggering release of histamine from mast cells
- Enhances clearance of antigen-antibody complexes
What are some of the roles of antibodies in an immune response to a pathogenic microbe?
Neutralize bacterial toxins and viruses Opsonize particles Activate complement Activate NK cells Activate basophils and eosinophils
Which receptors on a phagocyte recognises an opsonized cells?
C3b & Fc-epsilon
What happens to a mast cell on recognition of a pathogen?
- Triggers innate receptors and degranulation of the mast cells
- Mast cell goes to adaptive IS, and T/B/plasma cells sensitize the mast cells with pathogen specific IgG or IgE. There is then proliferation of these mast cells
What are some effects of Mast cell activation?
Contraction of smooth muscle, recruitment of dendritic cells, activation of macophages
Which cells initially respond to a Candida albicans infection?
CD4, neutrophils, macrophages, monocytes and DC
Which interleukin causes Th17 production?
IL-6, which leads to neutrophil activation
Which interleukin causes Th2 production?
IL-4
How does a T-cell and natural killer cell recognise a virally infected human cell?
Normal human cells express human leukocyte antigens (HLA) on their surface, which T-cells recognise.
Virally infected cells have downregulated HLA, and express viral peptides on the surface.
T-cells recognise the foriegn material, and NK cells recognise the HLA downregulation
Which APC educates CD8+ cells, and which MHC class are CD8 cells?
Dendritic cells CD8+ cells are MCH class 1
