What I would say is 'cell mentioned in q stem (it will probably be virally infected) presents antigen on MHC 1 marker to naiive t cell/cytotoxic t cell. Activated T helper cell with specific and complementary receptor to x antigen encounters naiive t cell and activates naiive t cell/cytotoxic t cell via release of cytokines and interleukins.' and then go on with the rest of your response.
What I'm trying to say is that APC is not as defining of a feature in cell mediated immunity as humoral immunity.
While this is probably okay for VCE biology, I would be cautious about saying APCs are not a fundamental part of cell-mediated immunity.
The following stuff is outside the VCE course, but we know that dendritic cells (DC) are really the only cell capable of activating T cells as they have the correct co-stimulatory molecules. Thus, for a T helper or a cytotoxic T cell to be activated, they usually require antigen presentation by a DC (via cross-presentation for MHC I if DC is not infected itself) to be activated (but this is biology and there are always exceptions haha). If a T cell just binds antigen without any co-stimulation it is programmed to die via apoptosis.
So for T helper or cytotoxic T cell to be activated, it does require APCs. And once a T helper is activated it can then help activate a Cytotoxic T cell that is also bound to a DC (sometimes the DC alone does not provide enough activating stimulation and needs 'help').
It is thought that the T helper binds to the DC itself to help further activate the DC which can then better activate the cytotoxic T cell (td;lr immunology is really complex haha so don't worry if this isn't making much sense)!
Importantly, once activated, by usually both an APC and T helper, the cytotoxic T cell can then assert its effector function on a cell presenting the correct antigen on MHC I.
In activation of naive cytotoxic t cells, the APC will bind both the helper t cell and a naive cytotixic t cell specific to that antigen. This cytotoxic t cell will receive stimulation from both the APC and the helper t cell resulting in its clonal selection and subsequent differentiation and proliferation. These activated cytotoxic t cells will then travel throughout the host where they will bind to MHC class I molecules presenting their specific antigen, and initiate the death of these cells through the release of perforin to create a pore in the target cell and granzymes which enter through the pore and trigger apoptosis (intrinsic pathway).
This is a good description for VCE biology. Don't talk about all that dendritic cells stuff I just described! That was just a bit of extra info.
What exactly is the purpose of the introns
While they don't code for the protein they are important for gene regulation. They can also code for things called functional RNAs (not VCE info).