So, this is it, this is the last video for this lecture. We're going to wrap up a few issues and kind of, sort of summarize a little bit of what we've done. One of the things I wanted to wrap up first was how the developmental processes wind up leading to a B-cell. So, let's go back again to hematopoiesis, where we had a hematopoietic stem cell and we use GATA2 to tell it to begin to differentiate. Then so, we had a lin plus cell, when that happened we used ikaros to tell this to become a lymphoid cell. Now, it turns out that to determine a B-cell, we need something called BSAP. So, if this lymphoid cell receives BSAP, then I will go into a B-lineage development. The ironic thing is that if this turns into a plasma cell, that is one that secretes the antibodies, then it stops making the BSAP. If however is becomes a memory cell, then it continues to make the BSAP. So, that we have in the B-lineage something that keeps it dividing, developing, and keeps its options open but still means it's a B cell that's going to be the BSAP. Once a cell becomes a plasma cell it is committed. It has a finite lifestyle ban, it is going to produce antibodies over a period of several weeks, and then it will undergo apoptosis and frankly if it doesn't, If somehow or another I maintain this state with or without the BSAP, then I'm getting a B cell cancer cell. So, it's something that actually kind of think about when you're looking at lymphoid or other kinds of blood cancers. So, anyway hematopoietic stem cell gata two gives you Lin plus, ikaros makes you lymphoid, BSAP means you're a developing B cell and once you become a plasma cell and you're terminally differentiated you then turn it off. Well, okay, we are at the end of this lecture and the last thing I want to bring up again is a reminder that here we have my favorite antibody molecule and here we have the parts, the CDRs that recognize antigen. What we really want to make sure we do is have antibodies were the CDR's recognize foreign antigen but not self-antigen and that isn't necessarily as easy as you might think. When we were in the bone marrow, we got rid of any cells that recognize self antigens in bone marrow, but they get out they get into the body have they seen kidney antigens in the bone marrow? I don't think so. So, there is an ongoing process to make sure that these cells do not produce antibodies that will attack your own self-tissues. One, not the only but one element of this is surveillance by the T regulatory cell which will down regulate the activity of adaptive cells especially if it thinks they're attacking the wrong thing. There are other regulatory elements as well, we'll see developing B cells actually have receptors for FC stems, those receptors do something completely different from what they do in myeloid cells, they down-regulate to be self. Well, there's a reason for that think about it if you're making lots and lots and lots and lots and lots of antigen then maybe you don't need to make so much. So, if the FC stems bind to the B cell, the B cell says, "Oh there's plenty of antibodies around maybe I should lower my production." Maybe if it's a cell that hasn't started yet making antibodies, it might say, "Oh well maybe what I need to do is become a memory cell". So, that if you have antibodies around that can also tie up the antigens that stimulate the antibodies. One reason for having the measles mumps rubella vaccine in the United States not given until one year, is that during the first year, infants often have antibodies from their mothers against these antigens. So, if you give them a vaccine, mom's antibodies tie up the antigens before baby has a chance to make antibodies against it. In other parts of the world where measles is more endemic and more likely to kill a child, they will give the first vaccine at nine months and hope for the best and maybe they can follow up with a booster later on or not but at least maybe the kid will survive. So, this was kind of an academic lecture but it is of all the lectures I do things that have some of the most important supporting information you can have to do something practical to improve the health of everyone.