Immunity trouble.. :(

[duhherro]

MHCI = CD8 activation (cytotoxic)
MHCII = CD4 activation (helper)

If you can't remember you can use the rule of 8, where if you multiply the MHC number by the T cell number it has to equal 8 (1*8 and 2*4)

As for what happens in binding.

Flu vaccine is given. It has dead flu virus in it. The virus is taken up by an APC and broken down. It's displayed on the cell surface on MHCI and MHCII. T helper cells arrive and bind MHCII, being activated. They then bind to a B cell and activate the B cell. The T cell will dissociated from the B cell and continue activating other B cells. The activated B cell will produce antibodies or form a memory cell. Produced antibodies will go into the circulation and have a protective effect for when you do get infected with flu.

Ohhh, could you just expand a bit on the ..

MHCI = CD8 activation (cytotoxic)
MHCII = CD4 activation (helper)   parts

So if an APC displays a MHC 1 marker, does that mean cytotoxic T cells just come and bind to it and then puncture the APC's membrane and hence no antibodies are formed?

And when you mentioned about the T cell dissociating from a B-cell , does that mean just the B cell becomes unbound and then forms plasma cell/memories  and then the APC with the attached TH cell just binds to another B-cell and the process repeats til antibody levels are high enough to destroy all foreign stuff?

[Russ]

APCs display MHCI and MHCII. It's just that cytotoxic cells only bind MHCI and helper cells only bind MHCII.

If APCs display MHCI that means that they can be targeted for destruction, yes. However, destroying the APC will not prevent antibodies being formed (unless the APC also happens to be a B cell).

Yes. Once a B cell is activated it does not need to remain bound to the T cell. The T cell, once activated, does not need to remain bound to the APC, since the APC will be needed to activate other T cells.

[duhherro]

APCs display MHCI and MHCII. It's just that cytotoxic cells only bind MHCI and helper cells only bind MHCII.

If APCs display MHCI that means that they can be targeted for destruction, yes. However, destroying the APC will not prevent antibodies being formed (unless the APC also happens to be a B cell).

Yes. Once a B cell is activated it does not need to remain bound to the T cell. The T cell, once activated, does not need to remain bound to the APC, since the APC will be needed to activate other T cells.

Wow, never knew that destroying the APC will not prevent antibodies being formed, does this just mean that B cells happened to get stimulated by cytotoxic T cells too?

So when a B-cell gets stimulated by the T cell, does it just clone into millions/a lot of antibodies (1 B cell = a lot of antibodies specific to APC) ? And then the APCs will get bound by another TH cell and that process repeats again?

And speaking about antibodies, do they just simply restrict the movement of the APC so immune cells can destroy the APC more effeciently ?

[ligands]

APCs display MHCI and MHCII. It's just that cytotoxic cells only bind MHCI and helper cells only bind MHCII.

If APCs display MHCI that means that they can be targeted for destruction, yes. However, destroying the APC will not prevent antibodies being formed (unless the APC also happens to be a B cell).

Yes. Once a B cell is activated it does not need to remain bound to the T cell. The T cell, once activated, does not need to remain bound to the APC, since the APC will be needed to activate other T cells.

Wow, never knew that destroying the APC will not prevent antibodies being formed, does this just mean that B cells happened to get stimulated by cytotoxic T cells too?

So when a B-cell gets stimulated by the T cell, does it just clone into millions/a lot of antibodies (1 B cell = a lot of antibodies specific to APC) ? And then the APCs will get bound by another TH cell and that process repeats again?

And speaking about antibodies, do they just simply restrict the movement of the APC so immune cells can destroy the APC more effeciently ?

i don't think you are understanding the role of an APC, they are not part of the pathogen and are not targeted by antibodies/tc cells, they simply stimulate t helper cells

1 bcell may turn into 1billion plasma cells which may produce 1billion antibodies each with is specific to a ANTIGEN not a APC, a different APC with a different antigen will bind to a th cell in future infections for a different response.

antibodies just bind to a specific antigen - signals the non-specific immune system to increase the rate of phagocytosis

[duhherro]

Thanks ligands, certainly clarified the parts i have troubled with . On a note , if its regarding MHC 1 and cytotoxic T cells, how would there be a production of antibodies in this scenario?

[ligands]

Thanks ligands, certainly clarified the parts i have troubled with . On a note , if its regarding MHC 1 and cytotoxic T cells, how would there be a production of antibodies in this scenario?

there wont be any production of antibodies if t cytotoxic cells are produced. antibodies are only b cells.

[duhherro]

Thanks ligands, certainly clarified the parts i have troubled with . On a note , if its regarding MHC 1 and cytotoxic T cells, how would there be a production of antibodies in this scenario?

there wont be any production of antibodies if t cytotoxic cells are produced. antibodies are only b cells.

Ahh so in our body, there are Cytotoxic T cells already circulating and once a MHC 1 is displayed it will just bind to that APC and then it destroys it ?

[ligands]

Thanks ligands, certainly clarified the parts i have troubled with . On a note , if its regarding MHC 1 and cytotoxic T cells, how would there be a production of antibodies in this scenario?

there wont be any production of antibodies if t cytotoxic cells are produced. antibodies are only b cells.

Ahh so in our body, there are Cytotoxic T cells already circulating and once a MHC 1 is displayed it will just bind to that APC and then it destroys it ?

sort of, MHC 1 is shown by all molecules with a nucleus and is designed to distinguish self from non-self
t cytotoxic wont travel around binding to random antigens showing a non-self MHC marker unless of course it has been told to do so from the th cell.
that job is done by the non-specific immune system, eg. marcophages.
t cytotoxic are specific therefore have to be programmed, same as b cells to target 1 specific antigen otherwise they will not kill anything and are pretty much waiting to be stimulated.

[duhherro]

Thanks ligands, certainly clarified the parts i have troubled with . On a note , if its regarding MHC 1 and cytotoxic T cells, how would there be a production of antibodies in this scenario?

there wont be any production of antibodies if t cytotoxic cells are produced. antibodies are only b cells.

Ahh so in our body, there are Cytotoxic T cells already circulating and once a MHC 1 is displayed it will just bind to that APC and then it destroys it ?

sort of, MHC 1 is shown by all molecules with a nucleus and is designed to distinguish self from non-self
t cytotoxic wont travel around binding to random antigens showing a non-self MHC marker unless of course it has been told to do so from the th cell.
that job is done by the non-specific immune system, eg. marcophages.
t cytotoxic are specific therefore have to be programmed, same as b cells to target 1 specific antigen otherwise they will not kill anything and are pretty much waiting to be stimulated.

Ahh, so that means only if the immune cells know it needs a specific response if the 2nd line of defence isnt sufficient, it will put an MHC 1 to stimulate the 3rd line (cytotoxic) to help?

Thanks again ligand + Spice!! Great help although i am annoying you guys

[ligands]

Ahh, so that means only if the immune cells know it needs a specific response if the 2nd line of defence isnt sufficient, it will put an MHC 1 to stimulate the 3rd line (cytotoxic) to help?

Thanks again ligand + Spice!! Great help although i am annoying you guys

yes and no, its generally going to go back to 3rd line because it much more efficient than the 2nd line is nearly all cases. because the 3rd line is actively looking for this specific antigen, whereas the 2nd line is more random and it may bump into whatever antigen and isn't as reliable because of that.

[duhherro]

Ahh, so that means only if the immune cells know it needs a specific response if the 2nd line of defence isnt sufficient, it will put an MHC 1 to stimulate the 3rd line (cytotoxic) to help?

Thanks again ligand + Spice!! Great help although i am annoying you guys

yes and no, its generally going to go back to 3rd line because it much more efficient than the 2nd line is nearly all cases. because the 3rd line is actively looking for this specific antigen, whereas the 2nd line is more random and it may bump into whatever antigen and isn't as reliable because of that.

Hmm didn't quote catch that part, did you mean that when an APC engulfs the foreign particle, does it just immediately put up a MHC 1 marker?

And on a sidenote, how do memory cells even work? Do they just instantly produce antibodies when the same pathogen is encountered in the body by the same antigen on MHC marker?

[ligands]

so all cells will have a MHC 1, they don't pop up or anything
seems that the 2nd line is not stimulated to target certain antigens it may only destroy 500 (example) foreign antigens compared to the 3rd line which may kill all the same antigen in 1 hit, 5000 at a time so it is much more reliable

for memory cells we just need to know that for subsequent infection by the same antigen there will be a much faster and stronger response - these questions are generally graph type questions

[duhherro]

so all cells will have a MHC 1, they don't pop up or anything
seems that the 2nd line is not stimulated to target certain antigens it may only destroy 500 (example) foreign antigens compared to the 3rd line which may kill all the same antigen in 1 hit, 5000 at a time so it is much more reliable

for memory cells we just need to know that for subsequent infection by the same antigen there will be a much faster and stronger response - these questions are generally graph type questions

I see so whenever there is a serious pathogen, it usually always stimulates the 3rd line then?

[ligands]

pretty much, or for any antigen that has not already been stimulated the antigen is presented for a response

[itsdanny]

The T cell, once activated, does not need to remain bound to the APC, since the APC will be needed to activate other T cells.

APC activates other T cells? What other T cells can this APC activate? The T cell that it just activated, is only specific to that APC (which has the antigen-MHC complex presented on the surface of its membrane). So why are there other T cells binding to that APC?

EDIT:
Oh, unless you mean the CD8+ T cells that is specific to that APC (and not OTHER T cells)? That makes sense. Otherwise, could you please elaborate further, thanks.