How do we eliminate pathogens that live outside cells?

Question 1

* overview of how general immune response works, e.g. for cut in the arm? *

Answer 1

make cells in: bone marrow (B-cells) and thymus (T-cells, CD4 & CD8) - primary lymphoid tissue. sit there until immune response required

cut happens:

• inflammation - acute localised inflammation iniates immune response
• blood vessels becomes leaky at site of injury - swelling from also makes **lymph node swell
• lymph node acts as a net (draining lymph node)** - catching anything thats come in from site of injury
• dendritic cells go from cut site to the draining lymph node - hold out pathogen in **MHC molecules - recognised by T cells
• **T cell clonal expansion

Question 2

what is general difference between response for extracelluar vs intracellular pathogens?

Answer 2

• *extracellular**: humoral immune response. secretion of:
• antibodies
• complement proteins
• antimicrobrial peptides
• *intracellular:** can’t secrete cuz pathogen is inside cell
• cytotoxic t cells
• NK cells
• T cell-dependent macrophage activation

Question 3

B cells make X?

Answer 3

antibodies - stick to antigens

Question 4

when do B cells secrete / not secrete antibodies

Answer 4

• *antibodies are tethered to B-cell** (not secreting antibodies yet) after maturation - when theyre mature niave B cells
• *antibodies are released** when infection occurs and are activated. activated B cells

memory B cells: dont secrete antibodies / resting

Question 5

which is the Fc end of an antibody - what does it do?

Answer 5

• Fc - bottom of Y bit
• dictates the function of antibody once bound to antigen
• has different isotypes: IgM, IgD, IgG, IgA, IgE

Question 6

where are the variable regions of antobody?

what is the miracleof the immune system?

Answer 6

fragment antigen-binding (Fab fragment)

• *miracle of immune system:**
• have billions of different B cells
• each one secretes a different antibody molecule
• so we have all antibodies which recognise nearly ALL possible pathogens - mixing and matching of genes

Question 7

role of dendritic cells?

Answer 7

DCs are specialised to capture and process antigens, converting proteins to peptides that are presented on major histocompatibility complex (MHC) molecules recognised by T cells.

• dendritic cells go around tissue, continually monitoring and assessing environment by processing proteins into peptides.
• in prescence of pathogen - PAMPS are activated by dendritic cell.
• dendritic cells go down afferent lympahtics to lymph nodes
• hold proteins out on MHC Class 1/2 molecules.
• if recognised by CD4/8 - clonal expansion and cytoxic fun happens

Question 8

how do you get generation of antibody diversity?

Answer 8

• variable gene selection when making different chains (heavy and light) of antibody:
• have V, D, J and C regions - all selected differently: combinational diversity
• also junctions are different: more diversity

therefore:
- different gene sequence - different a.a. - different shape to antibody binding region is different :)

have millions of antibodies!

Question 10

which antibodies are monomers, dimer and pentamer?

Answer 10

Question 11

basic overview of what happens when B cells are activated?

Answer 11

• Antigen binds to FAB bit of antibody
• Activates B cell: turns into a **plasma cell - produces lots of IgM
• **T cell help activating B cells
• other IGs are made later (IgG, IgA, IgF)

Question 12

what are 5 roles of antibodies once activated?

Answer 12

• *- neutralization**
• agglunation (the clumping of particles)
• Opsonization: coat pathogens that allow other immune cells to come and kill
• *- antibody dependent cell killing
• activation of compliment cascade**

Question 13

what is affinity maturation? where occur?

Answer 13

making better antibodies:
when a B cell makes an antibody a ‘better-fit’ to an antigen. Occurs at the germinal in lymph node and spleen

Question 14

what is the complement cascade?

Answer 14

another system of secreted proteins that is good at getting rid of extracellular pathogens, like bacteria.

• surface of bacteria can bind to complement proteins
• forms a pore on bacteria
• pops them !

The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen’s cell membrane.