Grant: Discovery Grants Program - Individual

Monocytes are pleiotropic myeloid immune cells that play a critical role in the initiation and coordination of innate immune and homeostatic regulatory processes, as well as acting as an important reservoir for specialized immune effector and antigen presenting cells (ie. macrophages and dendritic cells). Although they can be activated through a variety of mechanisms, the cytokine tumour necrosis factor (TNF) is fundamental in the regulation of this process, acting in both a paracrine and autocrine manner. Well-known to amplify and sustain monocyte responses following stimulation, recent work indicates that TNF may also mediate the gradual return to a resting state via the repression of NFkB, a mechanism known as TNF-tolerance. Since TNF can act as both "fuel" and "extinguisher" during monocyte responses, the regulation of mechanisms governing TNF-mediated activation and tolerance is of exceptional importance. Studies performed in a number of mammalian species indicate that monocyte phenotype and function is broadly impacted by aging. However, unlike the common and oversimplified conception that transitions from childhood to adulthood to old age invariably results in a reduction in cellular immune function, monocytes exhibit a variety of alterations with age. One such feature is a dysregulation of canonical signalling pathways such as the aforementioned NFkB, which are often shown to be over-active at a resting state and under-responsive when stimulated; cytokine production generally follows suit. How TNF-signalling is related to these perturbations is very much unknown, but we hypothesize that it plays a fundamental role. Hence, in the following proposal we aim to investigate the dynamics of TNF-mediated activation and tolerance in the regulation of monocytes and how it changes with age. Specifically, we will: 1)Investigate the age-related responses of monocytes to exogenous TNF. 2)Examine the phenotype and TLR-responses of young and old monocytes following TNF pre-exposure. 3)Determine if TNF pre-exposure impacts monocyte to macrophage differentiation and subsequent function. This comprehensive research plan will not only further our knowledge of the regulatory mechanisms governing monocyte activation, it will generate novel findings regarding their evolution with age. Furthermore, it will serve as a multidisciplinary platform for highly qualified personnel (HQP) training in areas such as cellular and molecular biology, immunology, and bioinformatics. Overall, this represents a fundamental component of our overarching goal to advance knowledge of the cross-talk between monocytes and their microenvironment, and specifically, how immunological factors mediate this process.