Do T Killer cells respond to antigens?

[SysBio]

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My question comes from AAMC 11, Biology Passage 3, second last question:

The question asks what do the receptors on the cytotoxic T lymphocytes (CTLs) respond to? I thought it would be growth factors from T helper cells (Ans: B), but apparantly the answer is that they would bind antigens on virus-infected cells (Ans: A).

I dont know much about the immune system but the Princeton Review Biology section explicity states that T killer cells do not respond to antigens themselves.

Is this an error by AAMC, Princeton Review, or are the cells in question not T killer cells?


(Mods: I think we are supposed to post AAMC q's in the specific threads but I cant find any for MCAT 11)

 

[Ssina]

I think AAMC is right... Tc have to somehow know that the cell is infected so they use MHC I molecules, that are presenting antigens (basically chunks of the virus on the membrane)... this is directing from the infected cell... and in contrast to Th cells that use MHC II from Antigen Presenting Cells (macrophages, etc)

in addition to maturation by the Th

 

[SaintJude]

Yeah AAMC is right (but what's new?)

Antigen binding causes cytotoxic T-cells to multiply and attack inoculated cells.

The T-helper cell growth factor acts to signal proliferation of more T-helper cells or aid in differentiation of T-lymphocyte cells into different types of T-cells.

 

[SysBio]

I went back and re-read PR, and it does NOT say that T killer cells do not respond to antigens....so I dont know where I got that from

thanks for the clarification guys!

 

[MedPR]

CD8 cells do not "see" free floating antigens. That's why the immune system requires antigen presenting cells (b cells, macrophages, dendritic cells, fibroblasts, glial cells, etc). When an immature T cell (CD4 or CD8) is "shown" the antigen by one of the APCs, it differentiates into a CD4 (T helper) or CD8 (Killer T cell). There are multiple types of Th cells, some secrete cytokines, some help to maintain antigen affinity (memory), and some prevent the immune system from continuous or excessive reaction (prevention of autoimmune disease).