Now, once a pathogen actually enters the tissue of our body, what happens is nearby cells called mass cells, which are basically cells that are physically situated in our tissue around that area begin to secrete special types of chemicals known as cytokines as well as histamine. And these chemicals basically help dilate the blood vessels that lead to the infected area and we'll see why that's important in just a moment. So mast cells are situated within the tissue and release histamine and other chemicals called cytokines that promote inflammation. And actually, as we'll see in the next lecture what cytokines also do is they actually bridge the innate immune system with adaptive immune system it basically promotes the interaction between the two different divisions of our immune system. While the histamine, what that does is it actually dilates our blood vessels and it also makes the capillaries more permeable to water. Now, along with the mass cells we have these basicil cells which are granulocytes and which travel within our blood.