Immunoglobulins did not arise in evolution to fight infection

The immune system in contemporary mammals is bewilderingly complicated. It comprises B-lymphocytes, various classes of T-lymphocytes, a complement system, and so on. The problem here is that it is difficult to see the wood for the trees. In order to appreciate the genuine complexity of this system, I will argue that it is necessary to deliberately and drastically simplify our perception of the system. In order to simplify, I propose to adopt an evolutionary approach: evolutionarily primitive systems offer privileged cases because they are simple cases. The key feature I will focus on is that immunoglobulins are “variable-region molecules”, produced by a specific process of somatic recombination and mutation. It follows that the “repertoire” of immunoglobulins will be “complete”; and a direct corollary of this is that immunoglobulins recognize each other, leading to the formation of an “idiotypic network”. I will illustrate the functioning of such a network by computer simulations based on a simple model. Antigens – in the first instance, macro-molecules of the body which houses the immune system – will be integrated into this network in harmonious fashion.
This approach leads to a reversal in perspective. Classical immunology is based on a military metaphor: the immune system destroys whatever it perceives.