The innate immune system declines with age, just like the adaptive immune system. The details are different: "The innate immune system is composed of a network of cells including neutrophils, NK and NKT cells, monocytes/macrophages, and dendritic cells that mediate the earliest interactions with pathogens. Age-associated defects are observed in the activation of all of these cell types, linked to compromised signal transduction pathways including the Toll-like Receptors. However, aging is also characterized by a constitutive pro-inflammatory environment (inflamm-aging) with persistent low-grade innate immune activation that may augment tissue damage caused by infections in elderly individuals. Thus, immunosenescence in the innate immune system appears to reflect dysregulation, rather than exclusively impaired function." Understanding the cause of the problem steers the search for solutions. Dysregulation means that the focus is on fixing errant signaling mechanisms, or on finding ways to directly instruct cells to act or not act. Cell transplants or repairs are not much use if the problem actually lies in the control systems.