Plasmablast and Plasma Cell Production and Distribution in Trout Immune Tissues

Abstract

These studies describe the in vitro and ex vivo generation of plasmablasts and plasma cells in trout (Oncorhynchus mykiss) peripheral blood and splenic and anterior kidney tissues. Cells were derived either from naive trout and cultured with the polyclonal activator, Escherichia coli LPS, or from trout that had been immunized with trinitrophenyl-keyhole limpet hemocyanin. Hydroxyurea was used to resolve populations of replicating (plasmablast) and nonreplicating (plasma cell) Ab-secreting cells (ASC). Complete inhibition of Ig secretion was only observed within the PBL. Both anterior kidney and splenic lymphocytes possessed a subset of ASCs that were hydroxyurea resistant. Thus, in vitro production of plasma cells appears to be restricted to the latter two tissues, whereas peripheral blood is exclusively restricted to the production of plasmablasts. After immunization with trinitrophenyl-keyhole limpet hemocyanin, specific ASC could be isolated from all immune organs; however, the anterior kidney contained 98% of all ASC. Late in the response (>10 wk), anterior kidney ASC secreted specific Ab for at least 15 days in culture, indicating that they were long-lived plasma cells. Cells from spleen and peripheral blood lost all capacity to secrete specific Ab in the absence of Ag. Late in the Ab response, high serum titer levels are solely the result of Ig secretion from anterior kidney plasma cells.

Differential compartmentalization of memory B cells versus plasma cells in salmonid fish

“…However, plasmablasts entering the circulation can, like their mammalian counterparts, become LLPCs upon reaching the survival niche stroma of the anterior kidney. The LLPCs then become the primary source of the serum antibodies [32,33]. Although stromal cell support of antigen-induced B-cell differentiation has yet to be demonstrated for trout, splenic and anterior kidney stromal cells have been isolated and demonstrated to foster trout lymphoid, erythroid and myeloid differentiation in vitro [53,54].…”

“…Analysis of ASC activity revealed a relatively heavier involvement of the spleen during the primary response, than in the secondary. Past studies [32,33] and the HU analysis with this study (Fig. 5) would suggest that, earlier in the response the spleen is also more active with plasmablast activity, while the anterior kidney is more active late in the response with PCs.…”

“…This technique permitted enumeration of non-replicating, antigen-insensitive, PCs [32,38] ( Fig. 3A-D).…”

“…For example, perhaps the requisites for exceptionally high-titered, extensively mutated, high-affinity responses in * These authors contributed equally to this work. [32][33][34], which home to their respective hematopoietic tissues, even though the organs themselves are different (i.e. bone marrow versus anterior kidney).…”

“…The membranes were then blocked in a 0.5% BSA in PBS for 1 h at RT. Development of the ELISPOTs was as described [32].Plasma cell numbers were determined by the ex vivo suspension of lymphocytes in tissue culture medium (TCM) in the presence of 100 mM hydroxyurea (HU) without antigen. HU is an inhibitor of DNA replication [59], thus enabling the resolution of plasmablasts (HU-sensitive, replicating ASCs) from PCs (HUinsensitive, nonreplicating ASCs) [32,38].…”