Immunogenetics (2004) 56: 379–387 DOI 10.1007/s00251-004-0697-7 BRIEF COMMUNICATION Chongbo He . Eric Peatman . Puttharat Baoprasertkul . Huseyin Kucuktas . Zhanjiang Liu Multiple CC chemokines in channel catfish and blue catfish as revealed by analysis of expressed sequence tags Received: 1 April 2004 / Accepted: 13 June 2004 / Published online: 7 August 2004 # Springer-Verlag 2004 Abstract Chemokines represent a superfamily of chemo- tactic cytokines involved in recruitment, activation and adhesion of a variety of leukocyte types to inflammatory foci, as well as in the organization and maintenance of lymphoid organ architecture and in normal developmental processes. Nearly all chemokines have been identified in human and mouse, but only a handful of fish chemokines have been identified. Here we describe 14 distinct chemokines from channel catfish and blue catfish identified by analysis of 30,000 expressed sequence tags. Based on sequence analysis, sequence similarity, and the arrangement of the conserved cysteine residues, all 14 chemokines were identified as members of the CC subfamily. Phylogenetic analysis did not reveal clear evidence of orthology of the catfish and human or mouse chemokines. Similarity analysis indicated that nine of the 14 CC chemokines were identified for the first time in fish. The availability of this pool of catfish CC chemokines should facilitate rapid identification and phylogenetic analysis of CC chemokines from other fish and related species. Keywords Chemokine . Gene expression . Innate immunity . Fish . Catfish Chemokines can be functionally grouped into homeostatic and induced categories. The homeostatic chemokines are produced and secreted constitutively, and are involved in lymphocyte trafficking, immune surveillance and local- ization of lymphocytes with antigen in the lymphatic system. The induced chemokines are produced during infection and are involved in recruitment, activation and adhesion of leukocytes to the site of infection or injury (Neville et al. 1997; Secombes et al. 2001). They are structurally related small peptides, with the majority containing four conserved cysteine residues (for a recent review, see Laing and Secombes 2004). Based on the arrangement of these conserved cysteine residues (Ahuja and Murphy 1996; Murphy et al. 2000), chemokines were divided into four subfamilies: CXC, CC, C, and CX3C. Corresponding to these subfamilies of chemokine proteins, their coding genes were designated by SCY (for small inducible cytokines) followed by a letter, A, B, C, or D (for CC, CXC, C, and CX3C, respectively). The CXC and CC are the two major subfamilies. A large number of chemokines have been identified from mammalian species including 16 CXC, 28 CC, two C, and one CX3C chemokines (Bacon et al. 2003). Identification of teleost fish chemokines has been slow. To date, only a handful of fish chemokines have been identified and reported (CC chemokines summarized in Table 1, reviewed by Laing and Secombes 2004). Low sequence conservation during evolution, coupled with the small size of chemokines, has prohibited molecular cloning using hybridization-based approaches or amplifi- cation using PCR. The lack of fish chemokine gene sequences hinders accurate phylogenetic analysis of orthology. Efficient means for the discovery of fish chemokines are demanded for the studies of comparative immunology and for understanding the evolutionary processes of the immune systems of fish in general. In recent years, the adoption of genomic approaches, especially through the analysis of expressed sequence tags (ESTs), has allowed faster discovery of fish chemokines (Kuroda et al. 2003; Baoprasertkul et al. 2004). A number of fish chemokines have been described and phylogenetically analyzed in a recent publication by Huising and co-workers (2003a). A CXC chemokine most similar to the mammalian CXCL10 was reported from carp (Savan et al. 2003). A second carp CXC chemokine, C. He . E. Peatman . P. Baoprasertkul . H. Kucuktas . Z. Liu (*) The Fish Molecular Genetics and Biotechnology Laboratory, Department of Fisheries and Allied Aquacultures and Program of Cell and Molecular Biosciences, Aquatic Genomics Unit, Auburn University, 203 Swingle Hall, Auburn, AL, 36849, USA e-mail: zliu@acesag.auburn.edu Tel.: +1-334-8444054 Fax: +1-334-8449208