Affiliations: Center for Neuroscience, Free University of Brussels (VUB), Brussels, Belgium | Department of Medical Protein Research, VIB, Ghent, Belgium | Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
Note: [] Correspondence to: Ron Kooijman, Center for Neuroscience, Free University of Brussels (VUB), Laarbeeklaan 103, B-1090 Brussels, Belgium. Tel.: +32 24774461; Fax: +32 24774464; E-mail: ron.kooijman@vub.ac.be
Abstract: The polypeptide hormone prolactin (PRL) is produced by the anterior pituitary and is best known for its role in the development of the mammary gland and lactation. Whereas the pituitary is the most important source of PRL in serum, PRL is also produced elsewhere by for instance the decidua and leukocytes. Although PRL does not seem to be crucial for the normal function of the immune system in mice, it has been proposed that PRL may exert immunomodulating effects under stress or pathological conditions. We summarize the expression of leukocyte subsets expressing PRL and focus on the regulation of PRL expression under normal circumstances and in several disorders. The literature contains plenty of evidence that several types of leukocytes produce bioactive PRL. Furthermore, it is clear that regulation of PRL in leukocytes differs from that in the pituitary and PRL production in leukocytes can be regulated by cytokines and other stimulators of leukocytes. Several groups showed that PRL expression in leukocytes can be increased under pathological conditions and it has been speculated that leukocyte-derived PRL may contribute to hyperprolactinemia and exert immunomodulating effects.
