Humoral immune responses

Question 1

Why do mammal’s immune systems need to be complex?

Answer 1

Because we have lots of body compartments and have babies that grow inside us whom need protection after birth

• body compartments
• fetus and neonate

Question 2

What are acute phase proteins? What can they be used for in the lab?

Answer 2

• Proteins produced by the liver under the influence of interleukin-6 from mast cells of innate immune system
• CRP, fibrinogen and mannose binding lectin
• basically function to opsonise bact and activate the complement pathway
• test for CRP - indicates infection (non specific)

Question 3

What are the outcomes of the complement system?

Answer 3

1. MAC - punches bad cells causing them to lyse
2. Tag - opsonisation for recognition by macrophages and engulfing by phagocytosis
3. Activate inflam response by triggering mast cells to release histamine - recruit cells from bv
4. Enhance clearance of AG-AB complexes

Question 4

What are the microbial strategies used to evade complement activity?

Answer 4

1. Inhib alternate activity by making the bact cell surface acidic (sialylation) e.g. Neisseria sp.
2. Inactivate complement components by producing elastases e.g. Pseudomonas
3. Interfere w rec for complement components (C3b) which interferes w opsonisation and phagocytosis e.g. Steptococcus
4. Bind plasma proteins that negatively regulate complement activity (remember antibodies need to bind to bact antigens for the classical pathway to occur) - done by expressing Pra1 on cell surface e.g. Candida

Question 5

Describe structure of immunoglobulins (antibodies)

Answer 5

• antigen binding site
• binding to Fc receptors (receptors for immunoglobulins)
• complement binding site
• placental transfer

Question 6

What are the main immunoglobulins?

Answer 6

IgM = B cell rec, agglutination and opsonisation
IgG = complement and cell activation in tissues
IgA = mucosal antibodies
IgE = activation of eosinophils and mast cells
(more functions and subtypes but these are the main ones to remember)

Question 7

What do immunoglobulins/antibodies do?

Answer 7

• neutralise bact toxins and viruses
• opsonisation
• activate complement pathway
• activate NK cells (ADCC)
• activate basophils/mast cells
• activate eosinophils

Question 8

What are 3 ways antibodies can neutralise influenza virus?

How does the flu virus evade these mechanisms?

Answer 8

1. antibodies for HA1 blocks binding to sialic acid on host CM
2. antibodies for HA2 blocks fusion of endosome membrane w virus membrane therefore preventing release of virus into cytoplasm
3. antibodies for neuraminidase prevents sialic acid from being cleaved off the new viruses and therefore prevents new viruses being released

• basically, haemaglutination (HA) inhibiting antibodies are protective of the flu

Flu virus evades neutralising antibodies by changing ANTIGENETICITY by RECOMBINATION of diff strains of virus = variation

Esp true for HIV

Question 9

What’s interesting about rotavirus?

Answer 9

It is neutralised in the mucosal surfaces, therefore by IgA (mucosal protection), stimulated by vaccine and breast milk

Question 10

What popn is more susceptible to pneumococcal disease and why?

Answer 10

Elderly.
Low opsonophagocytic antibody response to pneumococcal polysaccharide vaccine

• Basically, when elderly ppl are vaccinated the produce insufficient antibodies for phagocytosis to occur and therefore for immunity to develop