Immunity trouble.. :(

[duhherro]

Hi guys , having a bit of trouble with T-helper cells, do they just immediately identify foreign pathogens or come into action when a macrophage puts up the MHC marker to stimulate T helpers ?

Thanks in advance!

[ligands]

generally it will be an APC (antigen presenting cell) that will stimulate the t helper cell and cause the cascade of events that follow

[duhherro]

generally it will be an APC (antigen presenting cell) that will stimulate the t helper cell and cause the cascade of events that follow

Thanks for the fast reply!


Are APC's just macrophages ? or jut any phagocyte?

[ligands]

dendritic cells are probably the most common (for VCE purposes anyway) i think the only function of the dendritic cell is to present antigens
then the macrophages is the next most common.

both do the same tho in terms of presenting the antigen

[duhherro]

dendritic cells are probably the most common (for VCE purposes anyway) i think the only function of the dendritic cell is to present antigens
then the macrophages is the next most common.

both do the same tho in terms of presenting the antigen

So dendritic cells are a type of lymphocyte?  Just engulfs a foreign particle, then display its own antigen? And how do they display their antigen and marker 1 or marker 2 etc?

[Russ]

DCs are technically a type of lymphocyte, but they're not typically discussed as such. When someone says lymphocyte, they usually refer to T/B cells.

DCs are excellent at phagocytosing material from the environment. It then gets degraded within the cell and the peptide fragments merge with empty MHCII molecules. The complex is then displayed on the cell surface. They can do the same thing with MHCI, just via a slightly different presentation pathway.

[duhherro]

DCs are technically a type of lymphocyte, but they're not typically discussed as such. When someone says lymphocyte, they usually refer to T/B cells.

DCs are excellent at phagocytosing material from the environment. It then gets degraded within the cell and the peptide fragments merge with empty MHCII molecules. The complex is then displayed on the cell surface. They can do the same thing with MHCI, just via a slightly different presentation pathway.

I see, cleared a lot! So then a T-helper comes and binds to it , which stimulates the profileration of B cells into plasma and B-memories? And at the same time, T cells will be stimulated, forming Cytotoxic and T-memories ? Could you just verify that for me haha ^^

[ligands]

yes, in an exam they seem to ask about the t helper cell integrating with bcells with clonal selection/expansion than integrating with tcells.

[Russ]

edit
^^
ligands beat me but here anyway

I see, cleared a lot! So then a T-helper comes and binds to it , which stimulates the profileration of B cells into plasma and B-memories? And at the same time, T cells will be stimulated, forming Cytotoxic and T-memories ? Could you just verify that for me haha ^^

Th cell binds and is activated. The Th cell then goes off to find a B cell and activates it. The B cell will either produce antibodies or become a memory cell. And yes, at the same time, CD8/Tc cells will be generated

[duhherro]

edit
^^
ligands beat me but here anyway

I see, cleared a lot! So then a T-helper comes and binds to it , which stimulates the profileration of B cells into plasma and B-memories? And at the same time, T cells will be stimulated, forming Cytotoxic and T-memories ? Could you just verify that for me haha ^^

Th cell binds and is activated. The Th cell then goes off to find a B cell and activates it. The B cell will either produce antibodies or become a memory cell. And yes, at the same time, CD8/Tc cells will be generated

Thanks!!! Whew I'm glad i'm right for once LOL. and HOLY hell, so now a TH cell binds to the engulfed particle but then leaves and activates B / T cell stimulation into cloning? !!!??

[ligands]

edit
^^
ligands beat me but here anyway

I see, cleared a lot! So then a T-helper comes and binds to it , which stimulates the profileration of B cells into plasma and B-memories? And at the same time, T cells will be stimulated, forming Cytotoxic and T-memories ? Could you just verify that for me haha ^^

Th cell binds and is activated. The Th cell then goes off to find a B cell and activates it. The B cell will either produce antibodies or become a memory cell. And yes, at the same time, CD8/Tc cells will be generated

Thanks!!! Whew I'm glad i'm right for once LOL. and HOLY hell, so now a TH cell binds to the engulfed particle but then leaves and activates B / T cell stimulation into cloning? !!!??

the TH cell binds to the antigen on the APC, it then releases cytokines (an interleukin of some sort i think, don't need to know that) that attract tc/bcells (the TH cell hasn't left the APC yet) and it then looks for the complementary fit for the antigen

in most of the practice exams so far its been mostly TH cell binding to an APC then attracting a bcell and you have to show it proliferates/differentiates ect more so than tc cells

[duhherro]

edit
^^
ligands beat me but here anyway

I see, cleared a lot! So then a T-helper comes and binds to it , which stimulates the profileration of B cells into plasma and B-memories? And at the same time, T cells will be stimulated, forming Cytotoxic and T-memories ? Could you just verify that for me haha ^^

Th cell binds and is activated. The Th cell then goes off to find a B cell and activates it. The B cell will either produce antibodies or become a memory cell. And yes, at the same time, CD8/Tc cells will be generated

Thanks!!! Whew I'm glad i'm right for once LOL. and HOLY hell, so now a TH cell binds to the engulfed particle but then leaves and activates B / T cell stimulation into cloning? !!!??

the TH cell binds to the antigen on the APC, it then releases cytokines (an interleukin of some sort i think, don't need to know that) that attract tc/bcells (the TH cell hasn't left the APC yet) and it then looks for the complementary fit for the antigen

in most of the practice exams so far its been mostly TH cell binding to an APC then attracting a bcell and you have to show it proliferates/differentiates ect more so than tc cells

(Image removed from quote.)

Hmm Ligands, I understood the part where you got up to the 'releasing cytokines that attract t/b cells ' so then the TH unbinds from the antigen on APC and starts to look for a complementary fit for the antigen? Just a bit unsure on what you mean by looking for a complementary fit for the antigen.

Excuse my thick head :S

[ligands]

for example if you have a flu vaccine with the flu antigen the dendritic cell/macrophage is going to engulf this and display it on there MHC 2 marker. the TH cell will then bind to this MHC 2 marker, if in this case its going to be a bcell, there going to find an antibody on the bcell specific to the antigen (complementary in shape to be able to bind), cannot have the same shape - will not bind obviously, similar to competitive inhibition in enzymes

im not the best at explaining things

[duhherro]

for example if you have a flu vaccine with the flu antigen the dendritic cell/macrophage is going to engulf this and display it on there MHC 2 marker. the TH cell will then bind to this MHC 2 marker, if in this case its going to be a bcell, there going to find an antibody on the bcell specific to the antigen (complementary in shape to be able to bind), cannot have the same shape - will not bind obviously, similar to competitive inhibition in enzymes

im not the best at explaining things

Don't worry, i understood that .


So the production of antibodies will also bind to the APC with the TH cell ? And antibodies simply just "limit the movement" of the APC so more phagocytes and destroy it easier?

Also , when you said about the "in this case MHC 2 - b cell" , does that mean if the TH cell that binds to an APC with MHC 1 will result in stimulation of the T- cell side of  immunity (cytotoxic + memory) ?

[Russ]

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.