Recent Research Projects

Role of innate immune components in mastitis (Naoki ISOBE)

Mastitis is a critical problem in the dairy industry. However, its treatment and prevention methods have not been established. Mammary gland has a local immune system consisting established and innate immunity. Mammary epithelial cells can detect bacterial components using toll-like receptors on the cell surface. Then epithelial cells produce and secrete innate immune factors such as beta-defensin and lactoferrin and lactoperoxidase into the milk. ß-defensin and lactoferrin attack bacteria directly and kill it. ß-defensin family consists several components containing lingual antimicrobial peptide (LAP). Lactoferrin absorb iron ion, resulting in the shortage of iron ion in the surrounding circumstances. As bacteria need iron ion for its proliferation, lactoferrin has a role in bacteriostatic function. Cathelicidin, one of antimicrobial peptides, is secreted by leukocytes. Mastitis recruits a number of leukocytes in mammary gland. Therefore, cathelicidin may be contained in milk and have important role on preventing mastitis. However, there is limited information about function of these innate immune factor and antimicrobial peptides in the Mammary gland.
　Mastitis is induced by the physiological dondition of animals such as hormone. We reported that estrogen during estrous stage induce slight increased somatic cell count and decreased milk yields.
　Mastitis is induced not only bacteral invasion into udder through teat canal but also bacterial components (lipopolysachrride, LPS etc.) transferred from inflamation site another organs such as uterus (endometritis). We reported that LPS infusion into uterus caused inflammation in the udder (Purba et al.,2020, Jaisue et al., 2022, 2023). Treatment of mastitis requires the administration of antibiotics. This requires identification of the infecting organism and selection of an appropriate antibiotic. However, it has been shown that the number of viable bacteria in milk decreases drastically during preservation after sampling (Hisaeda et al., 2016). This was found to be due to phagocytosis of neutrophils (Koshiishi et al., 2017). Therefore, we are developing a methods to suppress the function of neutrophils so that the number of live bacteria does not decrease.

Research Theme

Changes of immune molecules in milk during bacterial stimulation.
Role of antimicrobial components in the mastitis.
Changes in viable bacterial in mastitic milk during preservation and prevention of its decrease.
Mastitis caused by not viable bacteria.

Immune Functions in Avian Reproductive Organs (Takahiro NII)

Immunodefense systems in the reproductive and digestive organs play essential roles in maintaining the health, productive efficiency, and hygiene egg and meet production. The goal of our research is to enhance the reproductive functions and immunodefense functions in chickens.

We investigate the innate immune functions and its endocrine control in chicken reproductive organs. We have identified expression of Toll-like receptors and avian ß-defensins (AvBDs) in the male and female reproductive organs. Toll-like receptors recognize pathogen associated molecular patterns. AvBDs are the member of antimicrobial peptides that kill a wide spectrum of microorganisms. We showed novel findings that antimicrobial peptides and cytokines are expressed, and their expression was upregulated in response to bacterial components in the ovary and oviduct. Then, we have shown that proinflammatory cytokines also upregulate the expression of AvBDs. In the other study, we identified the expression of mucin and tight junction molecules, namely claudins, forming mucosal barrier in the oviduct. The expression of mucin was upregulated by bacterial components. The expressions of antimicrobial peptides, cytokines and mucosal barrier molecules are changed in the regressed oviduct during molting, probably due to decline of gonadal steroid levels. The intracellular mechanism by which the expressions of AvBDs and cytokines are regulated is now under investigation.