Growth hormone and fish immune system.

Area of Science:

• Immunology
• Endocrinology
• Fish Biology

Background:

• The immune system of teleost fish is influenced by various factors, including hormones.
• Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are crucial endocrine factors with potential roles in immune function.

Purpose of the Study:

• To review the immunomodulatory effects of GH and the GH/IGF-I axis in teleost fish.
• To explore extra-pituitary GH expression and paracrine actions within the fish immune system.

Main Methods:

• Review of existing literature on GH and IGF-I in teleost fish immunity.
• Analysis of studies investigating GH administration and its effects on immune parameters.
• Examination of in vitro studies on fish leucocytes exposed to GH and IGF-I.

Main Results:

• GH administration enhances non-specific and specific immune functions in fish, including cytotoxic, phagocytic, and lysozyme activities, as well as immunoglobulin production.
• The GH gene is expressed in extra-pituitary tissues, notably lymphoid organs.
• IGF-I stimulates proliferation and superoxide production in tilapia phagocytic leucocytes, suggesting a paracrine role.

Conclusions:

• GH and IGF-I are integral to the teleostean immune system, acting through paracrine mechanisms.
• Further research is needed to fully elucidate the complex interactions between GH, IGF-I, and other factors in fish immunity.