Growth hormone and prolactin expression in the immune system

Area of Science:

• Endocrinology
• Immunology
• Cell Biology

Background:

• Prolactin (PRL) and growth hormone (GH) are critical pituitary hormones involved in lactation and growth.
• Both PRL and GH are recognized as modulators of immune system responses.
• Leukocyte expression of GH and PRL suggests potential autocrine or paracrine functions in immunity.

Purpose of the Study:

• To investigate the production of PRL and GH within human leukocytes.
• To characterize the forms and biological activity of PRL and GH produced by immune cells.

Main Methods:

• Analysis of GH and PRL mRNA expression in human peripheral blood granulocytes.
• Detection and characterization of immunoreactive GH and PRL variants using molecular weight analysis.
• Assessment of biological activity using the Nb2 bioassay.

Main Results:

• Human peripheral blood granulocytes express GH and PRL mRNA.
• These granulocytes contain high molecular-weight variants (37 and 43 kDa) of GH and PRL, not pituitary-sized forms.
• No secretion of these variants or biologically active material was detected from granulocytes.
• Certain leukemic myeloid cells were found to secrete biologically active, 23-kDa pituitary-sized PRL.

Conclusions:

• Human granulocytes produce distinct, high molecular-weight variants of GH and PRL, but not the canonical pituitary forms.
• Leukemic myeloid cells can secrete biologically active, pituitary-sized PRL.
• These findings highlight differential production and potential distinct functions of PRL and GH in immune cells versus pituitary sources.