Immunoregulation

The immune system of higher vertebrates is a complex network of separate, interacting cell populations, each ontogenetically endowed with specific regulatory (inductive or suppressive) or effector functions. The products of at least two major gene clusters—the immunoglobulin structural genes and the genes of the major histocompatibility complex—are expressed as active and passive recognition structures on cells of the immune system and at least some of their secreted products. Macrophages play a critical role in the initiation of immune responses. Regulatory subsets of thymus‐derived lymphocytes interact with macrophages and with each other in the control of immune effector cells. At every level of the immune response, cell interactions require that these regulatory cells recognize gene products of the major histocompatibility complex. Due to recent technical advances, rapid progress is being made in identifying subsets of human immunoregulatory cells; those identified to date show strong functional homolgy to previously well characterized murine cell subsets.