Submitted to: Developmental and Comparative Immunology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/26/2006
Publication Date: 6/30/2006
Citation: Edholm, E.S., Stafford, J.L., Quiniou, S.M., Waldbieser, G.C., Miller, N.W., Bengten, E., Wilson, M. 2007. Channel catfish, Ictalurus punctatus, CD4-like molecules. Developmental and Comparative Immunology 32:172-187. Interpretive Summary: T cells are white blood cells that encompass several subsets that can be distinguished on the basis of their expression of particular cell surface markers. CD4 molecules are markers present on the major helper T cell subset in both mammals and birds. Recently CD4 was identified in 2 fish, pufferfish and trout. This paper describes the identification of two forms of CD4 molecules in channel catfish. It was also shown that those two CD4 molecules were expressed in T cells. This information will help us understand the immune system pathways used to clear pathogens.
Technical Abstract: Two CD4-like (CD4L) molecules have been identified in channel catfish, Ictalurus punctatus. Although phylogenetically related to other vertebrate CD4 molecules, they exhibit only 19% amino acid identity to each other. IpCD4L-1 encodes a predicted protein containing four immunoglobulin domains, a transmembrane region and a cytoplasmic tail containing a p56(lck) binding site. In contrast, IpCD4L-2 encodes for a similar protein with three immunoglobulin domains. The gene organization of IpCD4L-1 is very similar to that of other vertebrate CD4 genes, while the genomic organization of IpCD4L-2 is different. Southern blots indicate both catfish molecules are likely single copy genes and mapping studies show that both are found on a single Bacterial Artificial Chromosome suggesting close linkage. At the message level, IpCD4L-1 and -2 are expressed in various catfish lymphoid tissues and in non-B-cell peripheral blood leukocytes (PBL). Both messages are upregulated in concanavalin A (ConA) and alloantigen stimulated PBL, but not in lipopolysaccharide (LPS)-stimulated cultures. In contrast, they are differentially expressed among the catfish clonal T cell lines. While both molecules appear to be T cell specific, their functional significance in catfish is unknown.