A kidney-transplant patient experienced a cytotoxic rejection of the new kidney. Place the following in order for that rejection: (1) apoptosis occurs; (2) CD8⁺ T cell becomes CTL; (3) granzymes released; (4) MHC class I activates CD8⁺ T cell; (5) perforin released.

a. 1, 2, 3, 4, 5

b. 5, 4, 3, 2, 1

c. 4, 2, 5, 3, 1

d. 3, 4, 5, 1, 2

e. 2, 3, 4, 1, 5

Video transcript

Welcome back everybody. Our next question says which of the following statements about cytotoxic T cell action is correct. A they primarily function in tissue repair rather than immune response. B they induce apoptosis in target cells through perforin and grand enzymes. C they directly release antibodies to neutralize target cells or d they rely solely on cytokine release to eliminate target cells. Well, we have our very helpful name in this case to remember what these guys do. We have that name, cytotoxic toxic to cells. So that can help us remember the function of these particular T cells. So as we look through our answer, choices, choice A is pretty easy to rule out primarily function in tissue repair rather than immune response. Well, this one's pretty obviously wrong. These are cytotoxic T cells. They destroy abnormal cells and that is part of their or that is their function as part of the immune response. So choice A definitely not our correct answer. Choice. B they induce apoptosis and target cells through perform and graz IMEs. Well, this is a correct statement. Apoptosis we can recall is programmed cell death which yes, are cytotoxic cells do this. Um and they induces apoptosis by releasing these cytotoxic Granules perform in graz IMEs to destroy, to kill abnormal cells. Ones that are um infected with a pathogen or ones that have undergone cancerous changes. So it's always odd to realize that cells that kill other cells have an important role in the immune system. But there are cells that cannot be repaired, they just need to be destroyed. So as not to cause further harm in the body. In choice C, they directly release antibodies to neutralize target cells. Well, this is not the role of cytotoxic T cells. The cells that release antibodies are the B cells instead. So choice C not a correct statement. And then finally, in choice D, they rely solely on cytokine release to eliminate target cells. Well, cytokine release is one mechanism. They use cytotoxic T cells release some cytokines that activate macrophages that come and help destroy abnormal cells. But our statement here has the word solely. So that's the incorrect part of this statement because of course, as we saw in statement five and statement B, excuse me, they also induce apoptosis by directly releasing cytotoxic Granules. So that, so that's why choice D though a little more tricky is also incorrect. So once again, our correct statement about cytotoxic T cell action is choice B they induce apoptosis and target cells through perforin and grand thymes. See you in the next video