Humoral Responses to Infection

Question 1

What is humoral immune responses to infections as a broad definition?

Answer 1

Innate and adaptive immune responses mediated by soluble (cell-free) immune system

Question 2

Fill in the blank:

Bacteria induce ____ to produce ____, which acts on ____ to induce synthesis of ____-____ proteins.

Answer 2

Bacteria induce macrophages to produce IL-6, which acts on hepatocytes to induce synthesis of acute-phase proteins.

Question 3

Does C-reactive protein bind to phosphocholine on bacterial surfaces? If yes, what does CRP act as?

Answer 3

Yes, it acts as an opsonin and complement activator.

Question 4

MBL (mannose-binding lectin) binds to carbohydrates on bacterial surfaces. True or false?

Answer 4

True

Question 5

What are the 4 ways in which a microbe can evade complement activity?

Answer 5

1. Inhibit alternative pathway of complement activation
2. Inactivate complement components
3. Bind plasma proteins that negatively regulate complement activity
4. Impair opsonisation and phagocytosis

Question 6

What is the structure of an immunoglobulin?

Answer 6

It has an antigen binding domain, a complement binding site and placental transfer site - the last 2 binds to Fc receptors

Question 7

What is the relationship between hemagglutination-inhibiting antibodies and protection against influenza?

Answer 7

Higher hemagglutination-inhibiting antibodies numbers in the body increases the level of protection against influenza.

Question 8

How does opsonisation enhance phagocytosis?

Answer 8

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.

Question 9

Are elderly adults with lower opsonophagocytic antibody more susceptible to pneumococcal disease?

Answer 9

Yes - low opsonophagocytic antibodies are strongly correlated with low IgG antibody activity

Question 10

What are four mechanisms by which the complement pathway controls infection?

Answer 10

1. Activates MAC to lyse bacteria
2. Opsonizes pathogens
3. Actives inflammatory response by triggering release of histamine from mast cells
4. Enhances clearance of antigen-antibody complexes

Question 11

What are some of the roles of antibodies in an immune response to a pathogenic microbe?

Answer 11

Neutralize bacterial toxins and viruses
Opsonize particles
Activate complement
Activate NK cells
Activate basophils and eosinophils

Question 12

Which receptors on a phagocyte recognises an opsonized cells?

Answer 12

C3b & Fc-epsilon

Question 13

What happens to a mast cell on recognition of a pathogen?

Answer 13

1. Triggers innate receptors and degranulation of the mast cells
2. 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

Question 14

What are some effects of Mast cell activation?

Answer 14

Contraction of smooth muscle, recruitment of dendritic cells, activation of macophages

Question 15

Which cells initially respond to a Candida albicans infection?

Answer 15

CD4, neutrophils, macrophages, monocytes and DC

Question 16

Which interleukin causes Th17 production?

Answer 16

IL-6, which leads to neutrophil activation

Question 17

Which interleukin causes Th2 production?

Answer 17

IL-4

Question 18

How does a T-cell and natural killer cell recognise a virally infected human cell?

Answer 18

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

Question 19

Which APC educates CD8+ cells, and which MHC class are CD8 cells?

Answer 19

Dendritic cells
CD8+ cells are MCH class 1