So the air pathogeways of our lungs, like the trachea, the bronchi and our bronchial. So this is what a derivative cell actually looks like. It has these projections, these dendrites. So let's suppose some type of foreign antigen is found inside our tissue and it comes from, let's say, some type of bacterial cell, the same cell that we spoke of earlier. Now, what this centring cell does is it basically phagocytizes this antigen and it basically engulfs it. And the lysosomes break it down and a small part of it is then expressed, it's then displayed on this MHC class Two complex that is formed by the cell as shown in the following diagram.