Transcriptome Analysis of Immune Response of mIgM+ B Lymphocytes in Japanese Flounder (Paralichthys olivaceus) to Lactococcus lactis in vitro Revealed That IFN I-3 Could Enhance Their Phagocytosis

Abstract

B cells have recently been proven to have phagocytic activities, but few studies have explored the relevant regulation mechanisms. In this study, we showed that the Japanese flounder ( Paralichthys olivaceus ) membrane-bound (m)IgM + B lymphocyte population could phagocytose inactivated Lactococcus lactis with a mean phagocytic rate of 25%. High-purity mIgM + B lymphocytes were subsequently sorted to investigate the cellular response to L. lactis stimulation in vitro . Transcriptome analysis identified 1,375 differentially expressed genes (DEGs) after L. lactis stimulation, including 975 upregulated and 400 downregulated genes. Many of these DEGs were enriched in multiple pathways associated with phagocytosis such as focal adhesion, the phagosome, and actin cytoskeleton regulation. Moreover, many genes involved in phagolysosomal function and antigen presentation were also upregulated after stimulation, indicating that mIgM + B lymphocytes may degrade the internalized bacteria and present processed antigenic peptides to other immune cells. Interestingly, the type I interferon 3 ( IFN I-3) gene was upregulated after L. lactis stimulation, and further analysis showed that the recombinant (r)IFN I-3 significantly enhanced phagocytosis of L. lactis and Edwardsiella tarda by mIgM + B lymphocytes. In addition, significantly higher intracellular reactive oxygen species (ROS) levels were detected in mIgM + B lymphocytes following rIFN I-3 treatment. We also found that IFN I-3 significantly upregulated Stat1 expression in mIgM + B lymphocytes, and the enhancing effect of IFN I-3 on mIgM + B lymphocyte-mediated phagocytosis was suppressed by fludarabine treatment. Collectively, these results demonstrate that mIgM + B cell-mediated phagocytosis in the Japanese flounder is effectively triggered by bacterial stimulation, and further enhanced by IFN I-3, which itself may be regulated by Stat1.

Safety and Transcriptome Analysis of Live Attenuated Brucella Vaccine Strain S2 on Non-pregnant Cynomolgus Monkeys Without Abortive Effect on Pregnant Cynomolgus Monkeys

“…We did not examine the lymph nodes for the innate immune response due to our concern that the fixation of animals and the collection of blood may lead to unexpected abortion, and as a consequence, it may interfere with our evaluations on the safety of the S2 vaccine, since abortion is an important parameter in our evaluation in this study. The use of the peripheral blood for the isolation of lymphocytes for transcriptomic analysis is not new, as the use of the peripheral blood from pigs ( 30 ), dogs ( 31 ), Chinese geese ( 32 ), and humans ( 33 – 35 ), including patients with COVID-19 ( 36 ), have been well-documented.…”

Type I Interferon Regulates the Survival and Functionality of B Cells in Rainbow Trout

“…To date, whether type I or type II IFNs affect B cell functionality has been only addressed in fish in one study in which flounder ( Paralichthys olivaceus ) type I IFN was shown to enhance the phagocytic capacity of IgM + B cells as well as their production of reactive oxygen species (ROS) ( 45 ). In the current study, we have investigated the effects of both type I and type II IFN on IgM + B cells using rainbow trout ( Oncorhynchus mykiss ) as a model species.…”

Kinetics of T lymphocyte subsets and B lymphocytes in response to immunostimulants in flounder (Paralichthys olivaceus): implications for CD4+ T lymphocyte differentiation

“…Therefore, to obtain all CD4 + cells in peripheral blood leukocytes, the leukocytes were incubated with a mixture of CD4-1 and CD4-2 mAbs as the primary antibody. The method of isolation of CD4 + T cells was performed as previously described 55 . Briefly, after the primary antibody, the leukocytes were incubated with goat anti-mouse IgG magnetic beads (Miltenyi Biotech, Germany).…”