Molecular Immunology 38 (2001) 365 – 373 Molecular cloning of a C-type lectin superfamily protein differentially expressed by CD8 - splenic dendritic cells  Irina Caminschi a,b, *, Karen M. Lucas a,b , Meredith A. O’Keeffe a , Hubertus Hochrein c , Yacine Laa ˆbi a , Thomas C. Brodnicki a , Andrew M. Lew a,b , Ken Shortman a,b , Mark D. Wright d a The Walter and Eliza Hall Institute of Medical Research, PO Royal Melbourne Hospital, Melbourne, Victoria 3050, Australia b Cooperatie Research Centre for Vaccine Technology, Queensland Institute of Medical Research, Brisbane 4029, Australia c Medical Microbiology, Immunology and Hygiene, Technischen Uniersitat Munchen, Munich, Germany d The Austin Research Institute, Kronheimer Building, A&RMC, Studley Road, Heidelberg, Victoria 3084, Australia Received 17 July 2001; received in revised form 5 August 2001; accepted 6 August 2001 Abstract Dendritic cells (DC) are potent antigen presenting cells that activate naive T cells. It is becoming increasingly clear that DC are not a homogeneous cell population, but comprise different subpopulations that differ in ontogeny and function. To further the molecular characterisation of DC, we screened for genes that were differentially expressed amongst DC subsets and could therefore give insight into their varying biological functions. Using Representational Difference Analysis (RDA) we identified a gene (CIRE) that is expressed at higher levels in the myeloid-related CD8 - DC than in the lymphoid-related CD8 + DC. CIRE is a 238 amino acid type II membrane protein, of approximately 33 kDa in size, whose extracellular region contains a C-type lectin domain. Northern blot analysis revealed that CIRE is almost exclusively expressed in DC and was not detected in organs such as heart, brain, kidney, liver, and thymus. T cells failed to express message for CIRE, whilst B cells expressed very low levels. These data here further substantiated by Northern blot analysis of 18 cell lines of various origins (myeloid, macrophage, B and T cell) where only one cell line, which was of myeloid origin and could give rise to DC, expressed mRNA for CIRE. Semi-quantitative RT-PCR suggested that CIRE is down-regulated upon activation. CIRE shares 57% identity with human DC-SIGN, a molecule that has been shown to be the ligand of ICAM-3 and that is also a receptor that binds HIV and facilitates trans-infection of T cells. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: Rodents; Dendritic cells; Cell surface molecules www.elsevier.com/locate/molimm 1. Introduction Dendritic cells (DC) are the professional antigen presenting cells that have the unique capacity to acti- vate naı ¨ve T cells and thus induce immune responses (Steinman, 1991). It is now evident that there are different subpopulations of DC in both mouse and man, and that these can differ in the type of immune response generated (Banchereau et al., 2000; Fazekas de St Groth, 1998; Lanzavecchia and Sallusto, 2000; Moser and Murphy, 2000; Shortman and Caux, 1997; Steinman et al., 1997). In the mouse spleen alone, there are three DC subsets defined by their expression of CD8 and CD4, namely, CD8 + CD4 - , CD8 - CD4 + and CD8 - CD4 - (Vremec et al., 2000) and these appear to be the product of separate developmental streams (Kamath et al., 2000). Many functional differ- ences between the general classes of CD8 + and CD8 - Abbreiations: BSA, bovine serum albumin; CIRE, GenBank acces- sion number AY049062; CRD, carbohydrate recognition domain; DC, dendritic cell/s; mAb, monoclonal antibody/s; HRP, horse radish peroxidase; Ig, immunoglobulin; LPS, lipopolysaccharide; PE, phyco- erythrin; RDA, representational difference analysis; WEHI, Walter and Eliza Hall Institute.  A preliminary account of this work was presented at the 6th International Symposium on Dendritic Cells, Port Douglas, 2000. * Corresponding author. Tel.: +61-3-9345-2533; fax: +61-3-9347- 0852. E-mail address: caminschi@wehi.edu.au (I. Caminschi). 0161-5890/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII:S0161-5890(01)00067-0