R. Craig Findly
Senior Research Scientist
PhD, Yale University, 1978
The skin, gills, and gut of fish serve as portals of entry for bacteria, viruses and protozoa, and are the sites of initial contact between pathogens and host. In skin, mucosal antibodies play a major role in host defense and antibody secreting cells (ASC) in the skin epithelium are the source of mucosal antibodies that recognize and provide immunity against the protozoan parasite Ichthyophthirius multifiliis and other pathogens. The major lymphoid organ in fish is the anterior kidney, which serves as a site of B cell development as well as differentiation. In mammals, B cell differentiation, expansion and antbidoy affinity maturation occur in the germinal centers of the spleen, lymph nodes and secondary mucosal associated lymphoid tissue (MALT). Because fish do not have regional lymph nodes or MALT, we postulate that these processes may occur not only in head kidney and spleen, but also in niches found in the epithelia of the skin. A better understanding of B cell differentiation is important in work to develop much needed protective vaccines for fish. It is our hypothesis that putative niches in skin epithelium may serve a function analogous to mammalian germinal centers. Thus, differentiated B cells, which give rise to ASC, may arise from naive B cells either in peripheral sites, spleen, or head kidney, or all three. RT-PCR methods are being used to determine if expression of genes associated with B cell differentiation occurs following in vitro infection of skin explants. In teleosts the immunoglobulin heavy-chain classes were previously thought to include only mu and delta, but recently the immunoglobulin heavy-chain locus in zebra fish has been shown to contain a newly discovered isotype, immunoglobulin Z. It is possible that IgD and IgZ, if catfish also contain this isotype and it can be detected by PCR, are also utilized in response to infection by I. multifiliis. Work is also in progress to develop vaccines that protect against infection by I. multifiliis.
- Findly, R. C., Roberts, S. J. and Hayday, A. C. Dynamic response of murine gut intraepithelial T cells after infection by the coccidian parasite Eimeria. Eur J Immunol. 1993 Oct;23(10):2557-64.
- Dickerson, H. W., Clark, T. G. and Findly, R. C. Icthyophthirius multifiliis has membrane-associated immobilization antigens. J Protozool. 1989 Mar-Apr;36(2):159-64.
- Jones, K. A. and Findly, R. C. Induction of heat shock proteins by canavanine in Tetrahymena. No change in ATP levels measured in vivo by NMR. J Biol Chem. 1986 Jul 5;261(19):8703-7.
- Clark, T. G., Dickerson, H. W. and Findly, R. C. Immune response of channel catfish to ciliary antigens of Ichthyophthirius multifiliis. Dev Comp Immunol. 1988 Summer;12(3):581-94.