Abstract
It has been well established that the efficiency of the immune system declines with increasing age. Immunosenescence causes increased susceptibility to infectious diseases, and infection is, in fact, the third leading cause of mortality in people aged 65 and over [1]. As is clearly apparent from the other chapters of this book, there are many components of the immune system that can change with age, and are crucial to maintaining an effective immune system. The humoral immune system interacts with the other components, both as part of its own development and via its effector mechanisms. The most important function of B-cells is to produce antibodies, the indispensable soluble effectors of many functions. There are a number of different stages of development for B-cells and their antibodies (Fig. 1).