hello and welcome to learn a double prodigy for free with mr. s Drake this video is on the humoral response in immunity and that is linked to b-cells so we're going to be looking at B cells and antibodies in the humoral response now if you want to make notes just make sure you get some pen and paper and pause whenever you want to so first of all B lymphocytes also known as B cells these are lymphocytes which are white blood cells involved in the specific immune response meaning is all to do the response to particular antigens all emphasize are made in the bone marrow and the b-cells mature there too the humoral response is the response involving B cells and antibodies and the reason it's called humoral rather than the B cell response or antibody response is because an olden turn olden days turn for body fluids was humor and because the antibodies are soluble they transport around in the blood and other bodily fluids and that's how this term came about the humoral response because it's to do with antibodies which dissolve and a soluble in the blood so b-cell activation then we talked in an earlier video which I'll just link up here on antigens and lymphocytes though you actually have approximately 10 million different lymphocytes and they are able to create two different antibodies and what that means it is the antibodies that these b-cells have on their surface will be complimentary to ten million different antigens antigens will be in the blood if you have a foreign particle or pathogen and if they do collide with their complementary antibody on a visa the b-cell takes in that antigen by endocytosis and then presents it on its cell surface membrane so when this b-cell collides with a helper t-cell receptor this is going to activate the b-cell to go through clonal expansion and differentiation which is sometimes known as clonal selection so the b-cells going to remo ptosis and that would create large numbers of clones or identical B cells and those B cells will then differentiate into different cells so some will become plasma cells some will become memory and B cells so the plasma cells will be able to make the antibodies and the B memory cells can divide rapidly into plasma cells and if you are then re infected at the same pathogen or the same antigens detect in the blood you're able to make large numbers of these plasma cells very rapidly which can then make large numbers of antibodies rapidly so a bit more than about the memory B cells these cells can live in your blood and your body for decades whereas plasma cells are very very short-lived so the advantage is although the memory B cells do not make antibodies they can divide by mitosis and make plasma cells very very rapidly if they collide with an antigen they've previously encountered and that's what we're seeing here the primary response is the first time that this B cell takes in the antigen % on its surface and becomes activated it then either becomes plasma cells which make antibodies but some will become memory cells and these and stay in your body for decades but if that memory cell collides with the antigen that its complementary to it will then differentiate into more memory B cells but also lots of plasma cells very very rapidly so they then get lots of antibodies very very quickly and what that means is you should then be able to destroy the pathogen so quickly that you don't ever get symptoms and that's what we mean when we say we're immune to a pathogen so that is your active immunity you've been exposed to the pathogen to gain immunity and this graph is often shown to demonstrate this so we've got the concentration of antibody over time and the first time you're exposed to that pathogen you aren't able to produce as many antigens and antibodies sorry and you can't produce them as quickly it takes much much longer but you will then have that store of memory b-cells so if you are reinfected for a second time they will differentiate rapid into plasma cells to make large large quantities of antibodies in a very very short space of time and as I said that means you will be able to destroy the pathogen before you get symptoms so what are antibodies n so antibodies are pricings and they are a quarternary structure protein and are linked care to protein just so you can recap on protein structure it's four polypeptide chains we've got two short chains on the outside and two long chains on the inside right up here is the variable region and that's the part which will change in shape and it's that bit which will be complementary in shape to a particular antigen and that's where the antigen would bind the constant region is shown in red so that bit will always be the same it doesn't change the heavy chain is the name of the longer chains in the middle and they're heavier because they are longer and this scent is the shorter and lighter chain and as I said the bit of the top which is variable is where the antigen binds and the way then the antibodies are able to help destroy pathogens is by this process called agglutination so the antibodies will bind to the antigens to create an antigen antibody complex and antibodies are slightly flexible and because of that they're able to bind and then slightly twist and flex to attach to another antigen and the result of this is you get multiple antibodies attaching to multiple antigens and clumping together and that's what a gluten ation is they're gluing together and the reason that is helpful is if you've got a big clump of these antibodies with their antigen and therefore hopefully the pathogen it makes it easier the phaedra sites to be able to locate and therefore far more efficient at engulfing so in summary be lymphocytes will respond to foreign antigens and through clonal selection they'll end up releasing monoclonal antibodies and that is when mean by the humoral response clonal selection will Glenn create plasma cells and memory cells and the classroom cells release the antibodies whereas the memory cells will remain in the blood for decades and will then be able to produce the plasma cells very very rapidly if you reencounter and that antigen antibodies are quarternary proteins made up of four polypeptide chains the variable region of an antibody is unique in shape antibodies bind to antigens to create an antigen antibody complex and that will then lead to the restrict destruction of antigen or the pathogen through the gluten ation and that's it so if you would like to have a go some practice questions to test your knowledge then go to miss astra comm to practice those skills if you found this helpful today and do please give it a thumbs up