(Note: Some of this is well beyond VCE knowledge)
To add on, MHC restriction really refers to the concept that in the thymus, T cells are positively selected so they can interact with at least one of the MHC alleles expressed by that individual as T cells recognize both parts of the antigenic peptide and the MHC molecule itself. All the other T cells that cannot interact with MHC die.
MHC restriction has some important implications in transplants.
CD8 and CD4 interact with class I and class II MHC molecules, respectively, and are responsible for the class I or class II MHC restriction of these classes of T cells.
At a stage of development, the thymocytes are what we call 'double-positive' as they will express both CD8 and CD4. During, positive selection they will interact with either self MHC I or MHC II and downregulate either CD4 or CD8 respectively.
Ohhh so is that why for clinal stimulation of Naive T cells it is the APC presenting that antigen on MHC I marker instead of the free floating antigens which make naive B cells under VO clonal selection.
B cells can recognize 'native' antigen. It can be free-floating but sometimes it is bound on the surface of some special cells in the B cell follicle.
T cells on the other hand recognize a combination of self MHC and a processed peptide fragment. In short, T cells can only 'see' antigen when it has been presented to them on MHC. Thus, if you were just to expose the T cells to 'free antigen' they would not clonally expand.
Yes, pretty much. MHC restriction has been hypothesized to be involved in positive selection of T lymphocytes when considering clonal expansion because the requirement for MHC-associated antigen presentation for T cell activation accounts for the MHC restriction of T cell–B cell interactions.
I am not quite sure what you mean by this (I am a little tired so forgive me!) But yes, any B and T cell interaction is MHC restricted as the B cell acts as an APC and presents antigen on MHC to T cells to 'get help.'