Allergy and Immunology

Cytokines are low-molecular-weight proteins secreted by many cells, which can function as immune mediators. (If the cell of origin is a lymphocyte, these proteins are usually called lymphokines.) Many cytokines were originally named on the basis of an observed biological activity (eg, tumor necrosis factor and interferon), but most are multifunctional and act on a variety of target cells. These hormonelike compounds are capable of a wide range of immunologic activities, including either stimulating or suppressing various cells of the immune system. Despite the powerful in vitro activities of cytokines and the demonstration of increased levels of cytokines in tissues, serum, or other biological fluids, the role of cytokines in the pathogenesis of disease remains unknown but intensely investigated.1 One of the major controversies about assigning cytokines a role in disease pathogenesis is that there are still many questions about the optimum methods for measuring individual cytokines. The most.