VCE Biology Question Thread

[Biology24123]

Natural Killer Cells actual destroy the cells that don't have MHC I markers on them (cancerous/virally infected cells).

EDIT:6000th Reply

My mistake. Cancer cells don't have MHC I but virally infected cells do

[cosine]

Cancer cells do have MHC I markers guys. Infact, cancer cells produce antigenic fragments within the cell and present them on these MHC I markers, only to which Cytotoxic T cells will bind and destroy them. So unlike viruses who invade host cells to invade their MHC I markers, cancer cells are already cancerous, they are programmed to do it initially.

Own question: When the transmembrane antibodies of B cells bind with specific antigens, the complex is engulfed. I know the antibodies have antigen binding sites, but do these antibodies bind with antigens directly on the surface of pathogens? Can viruses bind with B cell antibodies? Because if you think about it, its not the best idea for B cells to engulf viruses, right? Same goes with phagocytes, can they engulf/do they engulf viruses?

[Biology24123]

Cancer cells do have MHC I markers guys. Infact, cancer cells produce antigenic fragments within the cell and present them on these MHC I markers, only to which Cytotoxic T cells will bind and destroy them. So unlike viruses who invade host cells to invade their MHC I markers, cancer cells are already cancerous, they are programmed to do it initially.

Not part of the course at all. But some cancers prevent the presentation of MHC I on the membrane. So we were both wrong

Own question: When the transmembrane antibodies of B cells bind with specific antigens, the complex is engulfed. I know the antibodies have antigen binding sites, but do these antibodies bind with antigens directly on the surface of pathogens? Can viruses bind with B cell antibodies? Because if you think about it, its not the best idea for B cells to engulf viruses, right? Same goes with phagocytes, can they engulf/do they engulf viruses?

We answered this quite a few times. Phagocytes can engulf viruses, how would antigens end up on the MHC II otherwise? Also, the B cell is not engulfed by the phagocyte after the B cell binds to the antigen. Viruses bind to B cell antibodies. B cells do not engulf antigens, they bind to antibodies on the surface

Read my post on your summary of the immune system

[vox nihili]

Cancer cells do have MHC I markers guys. Infact, cancer cells produce antigenic fragments within the cell and present them on these MHC I markers, only to which Cytotoxic T cells will bind and destroy them. So unlike viruses who invade host cells to invade their MHC I markers, cancer cells are already cancerous, they are programmed to do it initially.

Own question: When the transmembrane antibodies of B cells bind with specific antigens, the complex is engulfed. I know the antibodies have antigen binding sites, but do these antibodies bind with antigens directly on the surface of pathogens? Can viruses bind with B cell antibodies? Because if you think about it, its not the best idea for B cells to engulf viruses, right? Same goes with phagocytes, can they engulf/do they engulf viruses?

Completely right. They're actually starting to make cancer therapies that effectively enhance the T-cell response to cancers.

The complex isn't engulfed as far as I know. Will ask one of the immunology majors to correct me if that's wrong, but my understanding of it is that it just engages the receptor and that signals for the B-cell to expand.

B-cells can bind antigens from any source, be they surface molecules or cytoplasmic.

EDIT: Biology24123 got there first

[Biology24123]

Completely right. They're actually starting to make cancer therapies that effectively enhance the T-cell response to cancers.

The complex isn't engulfed as far as I know. Will ask one of the immunology majors to correct me if that's wrong, but my understanding of it is that it just engages the receptor and that signals for the B-cell to expand.

B-cells can bind antigens from any source, be they surface molecules or cytoplasmic.

EDIT: Biology24123 got there first

If i'm correct, B cells can be antigen presenting cells?. Is that part of the course?

[cosine]

Guys but B cells are antigen presenting cells? If B cells have MHC II markers, then what's the point of having them if they cannot engulf the pathogen and present its antigen? A khan academy video also said that B cells have transmembrane antibodies that will bind to a specific antigen on a pathogen, and this complex will be engulfed, then antigenic fragments presented on MHC II markers of the B cell. Then this B cells MHCII will bind with a Th cell TCR and thus will stimulate proliferation. Any thoughts ?

[cosine]

Hey guys,

Been working very hard on these notes, took me about 3 weeks to make them, over 10,000 words and 4 documents long. I included images and summaries of diagrams after each topic to help summarise the information. I hope you all enjoy, feel free to download them if you wish. xD

Part 1: https://www.dropbox.com/s/itzipgw01j2nnqh/Exam%20Notes%20P1.docx?dl=0
Part 2: https://www.dropbox.com/s/ynbfvz5kpsjzyva/Exam%20Notes%20P%202.docx?dl=0
Part 3: https://www.dropbox.com/s/vqt1begdj6o632h/Exam%20Notes%20P%203.docx?dl=0
Part 4: https://www.dropbox.com/s/q7phpti2e83rm6g/Exam%20Notes%20P%204.docx?dl=0

[cosine]

I know someone answered this earlier, but I have another question regarding it. If transplanted organs have different MHC I markers, the Cytotoxic T cells will kill them. But don't Tc cells needs to be activated by Th cells? And Th cells are activated when a macrophage presents the antigen on MHC II, so how exactly do these Tc cells get activated when we get an organ transplant?

[paper-back]

Do we need to know about C2, C3, C4 etc. plants?

Hey guys,...

Cosine, you're a legend!

[cosine]

Cosine, you're a legend!

Are the notes good?

And no, on the study design it says we do not need to know specifics about those plants. In VCE bio all plants photosynthesise the same way.. xD

[cosine]

I know someone answered this earlier, but I have another question regarding it. If transplanted organs have different MHC I markers, the Cytotoxic T cells will kill them. But don't Tc cells needs to be activated by Th cells? And Th cells are activated when a macrophage presents the antigen on MHC II, so how exactly do these Tc cells get activated when we get an organ transplant?

After doing some research:

When cells present nonself antigens on MHC I markers, if a specific Cytotoxic T cells comes into contact with this, it is activated much the same way as helper t cells are activated when phagocytes present MHC II markers to them. So when Cytotoxic T cells bind to a cell's MHC I markers that presents foreign nonself antigens, the T cell proliferates rapidly into memory T cells and effector T cells. These effector Cytotoxic T cells now recognise the MHC I markers of cells and kills them.

So when we receive an organ transplant, Cytotoxic T cells that have the specific TCRs recognise the MHC I markers of the transplanted cells, and are activated. Once activated, they start destroying the organ cells/tissue? So the humoral immunity is not involved in this process, right?

[Biology24123]

After doing some research:

When cells present nonself antigens on MHC I markers, if a specific Cytotoxic T cells comes into contact with this, it is activated much the same way as helper t cells are activated when phagocytes present MHC II markers to them. So when Cytotoxic T cells bind to a cell's MHC I markers that presents foreign nonself antigens, the T cell proliferates rapidly into memory T cells and effector T cells. These effector Cytotoxic T cells now recognise the MHC I markers of cells and kills them.

So when we receive an organ transplant, Cytotoxic T cells that have the specific TCRs recognise the MHC I markers of the transplanted cells, and are activated. Once activated, they start destroying the organ cells/tissue? So the humoral immunity is not involved in this process, right?

Cytotoxic T cells don't proliferate when they recognise foreign antigens on the MHC I. T helper cells activate cytotoxic T cells to proliferate. The cytotoxic T cell will just kill the infected cell.

[cosine]

Cytotoxic T cells don't proliferate when they recognise foreign antigens on the MHC I. T helper cells activate cytotoxic T cells to proliferate. The cytotoxic T cell will just kill the infected cell.

Okay so can you just clarify me with the transplanted organs?

How are cytotoxic T cells activated when we get foreign cells from a transplant? I know you just answered it, but like specifically for transplanted organs. Do macrophages engulf these transplanted cells, present antigens on the MHC II markers, activate T helper cells? And then these T helper cells will activate specific Cytotoxic T cells that will bind with the MHC I of the transplanted cells?

Cheers.

[Biology24123]

Okay so can you just clarify me with the transplanted organs?

How are cytotoxic T cells activated when we get foreign cells from a transplant? I know you just answered it, but like specifically for transplanted organs. Do macrophages engulf these transplanted cells, present antigens on the MHC II markers, activate T helper cells? And then these T helper cells will activate specific Cytotoxic T cells that will bind with the MHC I of the transplanted cells?

Cheers.

Don't need to know the specifics of graft rejection but you need to know the implications and why it happens

[Biology24123]

Okay so can you just clarify me with the transplanted organs?

How are cytotoxic T cells activated when we get foreign cells from a transplant? I know you just answered it, but like specifically for transplanted organs. Do macrophages engulf these transplanted cells, present antigens on the MHC II markers, activate T helper cells? And then these T helper cells will activate specific Cytotoxic T cells that will bind with the MHC I of the transplanted cells?

Cheers.

Also, in your notes it said that histamine is released after inflammation. Histamine is apart of the inflammatory response