I have been searching on the web to find the right answer to your question. From my results I can tell you that several scientists have long studied the immune system, imagining how many of the component cells proceed on their microscopic duties. Until recently, there has been no way to directly view much of this complex cellular teamwork in vitro and in real time. Scientists have discovered that there are many different kinds of dendritic cells and that each type is skilled in different ways for revealing what is otherwise invisible to the immune system at the infection site. I could not find the amount of dendritic cells, but they mention that there are many of them inside our bodies.

On the other hand, Harvard University researcher Ulrich H. von Andrian explains that the dendritic cells alert the T cells that there is something foreign entering the body, they tell the T cells what to do, how to respond. They have known about some aspects of this process from tissue culture studies, but this has never been observed before in vivo. That has largely been a black box.

Adrians group mentions that they have explored the first days after a T cell encounters the one antigen it will learn to recognize; during this time interval, T cells first migrate rapidly and touch every dendritic cell for only a few minutes. This initial phase lasts about eight hours. Then the T cells pick one antigen-presenting dendritic cell and sticks to it for many hours.

If you want to read the article, please go to the next URL. I hope this helps to answer your question.

dendritic_cells