Changes in lymphokine receptor expression and fatty acid composition of phospholipids and triacylglycerols in rat adipocytes associated with lymph nodes following a transient immune challenge J.D. Priddle * , C.A. Mattacks, D.A. Sadler, H.A. MacQueen, C.M. Pond Department of Biological Sciences, The Open University, Milton Keynes MK7 6AA, UK Received 4 April 2002; accepted 17 September 2002 Abstract Single-photon counting fluorimetry was used to record the time course of the expression of interleukin-10 receptors labelled with fluorescent antibodies on the surface of adipocytes over 24 h, following an immune challenge to the rat popliteal lymph node. Homologous perinodal and remote-from-node samples from the stimulated and unstimulated popliteal depots were compared in rats fed on plain chow and chow supplemented with 10% w/w suet, fish or vegetable oils. Receptor expression was maximal 6 h after stimulation, and returned to baseline after 24 h, and was similar in the stimulated and unstimulated depots. Fewer receptors were elicited in tissues from rats fed lipid-supplemented diets compared with the control diet, with fewest of all following the fish oil diet. These data suggest that interleukin-10 is involved in local interactions between perinodal adipocytes and lymph node lymphoid cells. Both triacylglycerols and phospholipids contained more polyunsaturates and fewer saturates in perinodal adipose tissue than in samples from sites not associated with lymphoid tissue. These data are consistent with paracrine interactions between perinodal adipocytes and activated lymphoid cells.  2003 Elsevier Science Ltd. All rights reserved. Keywords: Interleukin-10 receptors; Phospholipids; Site-specific properties; Perinodal adipose tissue; Lymph nodes 1. Introduction Adipose depots with lymph nodes embedded in them are found throughout the mammalian body and are particularly associated with potential portals of infec- tion, such as the gut. Many site-specific properties of perinodal adipocytes are consistent with the hypothesis that when lymph node lymphoid cells encounter an immune challenge, they stimulate nearby adipocytes to mobilize resources that provide for their immediate response and any subsequent cellular proliferation (Pond, 1999, 2002). Perinodal adipocytes secrete fatty acids (Pond and Mattacks, 1995, 1998) that could func- tion not only as metabolic fuel and precursors for the synthesis of various eicosanoid mediators in the immune system, but also as constituents of newly synthesized cell membranes (Calder, 1998). Peripheral immune processes are readily modified by dietary lipids (Sanderson et al., 1995) and may modulate the cells capacity to support receptors that recognise the paracrine signals that mediate local interactions with adipocytes. Thus, both the mediators of this interaction and the structure of the membranes that support them are potential targets for intervention in the functional relationship between adipose and lymphoid tissue and the metabolic support for immune processes. We have studied the popliteal depot of the rat because it contains a single lymph node that drains the hind limb (Smith and Morris, 1970). It is quiescent in the healthy animal, so can conveniently be used to study the effect of experimental immune activation of the node upon its surrounding adipose tissue. More prolonged immune challenges activate adipocytes situated further from the lymphoid tissue and increase their sensitivity to certain cytokines (Pond and Mattacks, 2002), but the * Corresponding author. Fax: +44-1908-654167 E-mail address: j.priddle@open.ac.uk (J.D. Priddle). Cell Biology International 27 (2003) 23–29 Cell Biology I nternational www.elsevier.com/locate/jnlabr/ycbir 1065-6995/03/$ - see front matter  2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S1065-6995(02)00253-6