Inflammation and tissue homeostasis

My name is Herman Waldmann. I'm from the Sir William Dunn School of Pathology and I am going to be coordinating this immunology series. The point of this introductory lecture, is to introduce you to the role of inflammation and immunity in relation to tissue homeostasis.

In other words, I want to be discussing how the immune system fits into the evolution of animals and the way animals function. When we think about it, multicellular organisms have generated diverse cells to perform different functions, and they specialize. It's very important for those various functions that they are well controlled and that requires mechanisms of sensing the amount of the product they make and also being able to affect a change in that product to ensure that the animal has adequate signals, not too many, not too little to enable those cells to function properly. For example, they can sense glucose and they can generate insulin or glucagon, they can sense oxygen, and generate erythropoietin in the case of higher animals. Is very important though, that these tissues that have specific functions have through evolution got to protect themselves against perturbations that could be from the outside, pathogens, toxins, or from inside, some damage from cell death or ischemia and so on. These functions also require homeostasis mechanisms that have become called inflammation and immunity. Protection of our tissues to enable them to function depends on a further interaction of the tissues with inflammatory cells and cells of the immune system with feedback pathways that will ensure effective function. The whole point being that the cells need to sense the presence of the perturbing signal, and in turn deliver effective signals to get rid of the disruptive agent and also having got rid of the disruptive agent to enable tissue integrity, to return, remodeling, repair, and so on. This need for protecting the tissues has driven the evolution of what we call the innate and adaptive immune system. The innate just protection against anything and develop an adaptive protection against very specific targets, which we referred to in immunology as antigens. The important thing is that this protection of the tissues mustn't penalize the host or the tissues that it's protecting. It has to be balanced and itself subject to homeostasis. Of course, pathogens and their toxins have been a key driver of such homeostatic mechanisms controlling inflammation and immunity.