“…Different subsets of B cells have been reported for different species: IgM + /IgD + /IgT − , IgM − /IgD + /IgT − and IgM − /IgD − /IgT + in rainbow trout (Castro et al, 2014;Ramirez-Gomez et al, 2012;Zhang et al, 2010) and IgM + /IgD − , IgM + /IgD + and IgM − /IgD + in channel catfish (Edholm et al, 2010;reviewed in Salinas et al, 2011). Most fish species have IgT orthologs, such as zebrafish (Danilova et al, 2005), rainbow trout (Hansen et al, 2005), fugu (Savan et al, 2005), carp (Ryo et al, 2010;Savan et al, 2005;Xiao et al, 2010) and salmon (Tadiso et al, 2011). To date, catfish is the only species where an IgT equivalent has not been identified.…”