So these antibodies circulate along our blood system and our lymph system until they basically bind to the specific antigen that is found on another pathogen or let's say, some type of bacterial cell. Now, once our antibody binds onto that antigen it can do two things. It can either call upon other leukocytes, for example, macrophages, to come and engulf that pathogen or it can begin to aggregate and form this very large insoluble complex in a process known as agglutination. So antibodies are very, very important and they're involved in the adaptive immune system. And that's exactly why we call it an adaptive immune system because we have these other types of cells known as memory B cells and we also have actually memory T cells as we'll see in a moment. And what these memory cells do is they store a copy of that antibody on the membrane of that memory cell.