Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2018
Publication Date: 1/1/2019
Publication URL: http://handle.nal.usda.gov/10113/6230182
Citation: Lange, M.D., Waldbieser, G.C., Lobb, C.J. 2019. The proliferation and clonal migration of B cells in the systemic and mucosal tissues of channel catfish suggests there is an interconnected mucosal immune system. Fish and Shellfish Immunology. 84:1134-1144. https://doi.org/10.1016/j.fsi.2018.11.014.
Interpretive Summary: Catfish farming remains number one among U.S. aquaculture production with annual revenues of $300-400 million dollars. As aquaculture production intensifies the frequency of infectious disease outbreaks among production systems will only continue to grow. Add to this an increase in the regulation of licensed therapeutants and resistance to available antibiotics means that alternative methods of infectious disease protection will be required. Vaccination against different fish pathogens has proven to be an effective management practice in reducing infectious diseases. The fish mucosal immune system has a critical role in conferring protection against fish disease. For this reason, additional work needs to be done to better understand the evolution of the mucosal immune system in fish. To this end a series of IgM cDNA libraries were made from different tissues derived from a single channel catfish and cDNA clones were sequenced to characterize the B cell repertoire. Individual and clonal B cells were identified and later used to examine interrelationships among the systemic and mucosal tissues. From this work we have concluded that an underlying mucosal immune system exists independently of the systemic system. We believe this information will aid in the development of new therapies and vaccines for use in the aquaculture industry.
Technical Abstract: IgM transcripts from different mucosal and systemic tissues from a single adult channel catfish have been evaluated. Arrayed heavy chain cDNA libraries from each of these different mucosal and systemic tissues were separately constructed, hybridized with VH family specific probes and a variety of approaches were used to define their structural relationships. Baseline hybridization studies indicated that the tissue libraries had different VH expression patterns, and sequencing studies indicated this was not simply due to varying proportions of the same B cell population. In the systemic tissues of PBL, spleen, and anterior kidney >95% of the sequenced clones in the arrayed libraries represented different heavy chain rearrangements. Diversity was also found in the mucosal libraries of skin, gill lamellae, and two non-adjoining regions of the intestine, but additional populations were identified which indicated localized clonal expansion. Various clonal sets were characterized in detail, and their genealogies indicated somatic mutation accompanied localized clonal expansion with some members undergoing additional mutations and expansion after migration to different mucosal sites. PCR analyses indicated these mucosal clonal sets were more abundant within different mucosal tissues rather than in the systemic tissues. These studies indicate that the mucosal immune system in fish can express B cell transcripts differently from those found systemically. These studies further indicate that the immune mucosal system is interconnected with clonal B cells migrating between different mucosal tissues, results which yield new insight into immune diversity in early vertebrate phylogeny.