SYSTEMIC FEATURES OF IMMUNE RECOGNITION

The gut is home to a great number of microbes. The immune system, to protect the body, must discriminate between the pathogenic and non-pathogenic microbes and respond to them in different ways. How the mucosal immune system manages to make this distinction is poorly understood. Here, we explore whether the decision to respond in a certain way to a microorganism is made by single types of cells and molecules or by the collective activity of various kinds of cells and molecules in a given anatomical compartment. We show here that the distinction between pathogenic and non-pathogenic microbes is made by an integrated system rather than by single types of cells or single types of receptors. Since immune recognition is constituted by a complex network of molecular and cellular level interactions, complete understanding of this process requires knowledge of these interactions. However, is it possible to explain immune recognition in molecular and cellular terms if this process is multiple realizable? Indeed, given the number and dynamics of elements involved in the recognition, it is hardly possible that their exact configuration could ever be reproduced even in the same individual. We argue that it is practically impossible to reduce immune recognition to its actual molecular and cellular realization. (This would require making reference to an infinitely long disjunction of lower level processes and each disjunct would be endlessly complex). Instead, the recognition is reducible to the approximation of molecular and cellular level processes. We suggest that the same strategy that was used by us to explain immune recognition in terms of lower level approximations is commonly applied by molecular biologists and systems biologists to explain complex biological processes.