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Daya, Sandeep; Davies, Heather; Colyer, Frances; Tuffnell, Joshua; Loughlin, Jane and MacQueen, Hilary
(2013).
Abstract
Many reports in the literature suggest the involvement of perinodal adipocytes in inflammatory immune responses taking place in immune-challenged lymph nodes. Triacylglycerols (TAG) from the diet accumulate in adipocytes, and pass to lymph node lymphoid cells where they are used to provision immune responses. These adipocytes are specialised: TAG in perinodal adipose tissue are relatively enriched in polyunsaturated fatty acids compared with adipocytes that are not in proximity to lymphoid tissue. Polyunsaturated fatty acids can be used as precursors of eicosanoids and other regulatory molecules, as well as for membrane biosynthesis and energy. Thus perinodal adipocytes are specialized to provision immune cell metabolism.
Dendritic cells are well known as antigen presenting cells. They are migratory and are found in lymph nodes, and in significant numbers among perinodal adipocytes. Their numbers are modulated by dietary fatty acids. Dendritic cells can induce primary immune responses and allow the establishment of immunological memory. They are known to interact with adipocytes in various situations such as Crohn’s disease, and it has been reported that developing dendritic cells accumulate lipid, which may derive from adipocytes. Thus dendritic cells are candidates for involvement in the transfer of TAG to lymphoid cells mounting an immune response.
Here we show by light and electron microscopy that small adipocyte-like cells are normal residents of the lymph node, and that following an immune challenge they are observed in association with dendritic cells deep within the stimulated node.
We also show in an in vitro co-culture system that both adipocytes and lymphoid cells exhibit altered metabolic activities when they are cultured together compared to when they are cultured alone. This is indirect evidence for a functional molecular interaction in vivo.
We propose that this co-localisation and putative interaction is the basis for provisioning a rapid immune response by dendritic cells. This phenomenon may therefore represent part of the mechanism for the development and/or deployment of immunological memory.