Thioredoxin acts as a B cell growth factor in channel catfish

To identify differentially expressed genes from channel catfish macrophages , a cDNA library from LPS-stimulated catfish macrophages was screened by su btractive hybridization. This screening yielded a 552-bp cDNA coding for ca tfish thioredoxin (CF-TRX). The deduced amino acid sequence revealed that C F-TRX contains 107 amino acids and is 59% homologous to human adult T cell leukemia-derived factor/TRX originally described as an IL-2R alpha -inducin g factor, Northern blot analyses showed that CF-TRS is expressed in catfish T and macrophage cell lines, but weakly in B cell lines. Similar results w ere also observed in Western blot analyses using a mAb specific for recombi nant CF-TRX (rTRX). The use of rTRX in functional studies demonstrated that rTRX induces in vitro proliferative responses of catfish PBL that were syn ergistically enhanced by the addition of culture supernatants from catfish T cell lines. In addition, cell separation studies and how cytometric analy ses revealed that the cells proliferating in rTRX-stimulated cultures mere mostly B cells. These results suggest that CF-TRY may have an important rol e in the activation and proliferation of channel catfish B cells.