Immune function

The immune system consists of two complementary response pathways: (1) the innate immune system and (2) the adaptive immune system. This tightly regul ated and complex system provides host protection to a massive array of pote ntially damaging microorganisms. When immune function is deficient, the hos t has increased susceptibility to infections. There are multiple cells and a vast array of humoral mediators and cell receptors that are necessary for a normal immune response, and defects in a number of these are responsible for the immune disorders discussed in this issue.