previously we said that b cells can encounter antigens that are just free floating in the body. But t cells need to be presented antigens and T cells are actually going to be classified as either Cd four plus or Cd eight plus based on whether they have a cd four or cd eight protein. Now these CD four Plus T cells Will interact with epic tokes bound to MHC Class two proteins. You can see this happening here and uh those MHC class two proteins remember are going to be found on antigen presenting cells like dendritic cells. And uh when these Cd 84 plus T cells are presented with Epic Tokes that they can interact with, they become activated. And these activated Cd four plus T T cells will undergo clonal expansion and form helper T cells. And uh the Cd eight plus T cells will interact with Pepitone apps on MHC one class proteins which are going to be found on most cells. So uh you know these aren't gonna be those specific antigen presenting cells like the dendritic cells and the B cells and the macrophages. Instead these are going to be found on just like your average regular joe sells. And it's going to if they combined to those episodes it's gonna activate those Cd eight plus T cells and those will undergo clonal expansion to form side a toxic T cells. So here behind me you can see the side a toxic T cells being formed from antigen presentation with an MHC one Class protein. And over here you can see helper T cells being formed from an interaction with an MHC class two protein. And remember these are going to be the antigen presenting cells like dendritic cells. No, basically what these guys are asking is show me what you got. So let's talk about what these types of cells do side a toxic T cells which sometimes abbreviated T. C. These are effect er T cells. And their job is to kill pathogen infective cells. This is basically a defensive measure against the pathogen. So if this cell, let's say uh has been infected and it is presenting the antigen from that pathogen, the psycho toxic or killer T cell will come over and induce cell death. It will induce uh you know the cell to die with that. Let's flip the page and talk about what helper T cells do.
