A complete regulatory loop between the immune and neuroendocrine systems.

Area of Science:

• Immunology
• Neuroendocrinology
• Molecular Biology

Background:

• Lymphocytes can produce adrenocorticotropin (ACTH) and endorphins.
• Lymphocyte-produced ACTH shares properties with pituitary ACTH.
• The immune and neuroendocrine systems may communicate via peptide hormones.

Purpose of the Study:

• To investigate the synthesis and activity of lymphocyte-derived ACTH.
• To explore the in vivo relevance of this immune-endocrine signaling.
• To examine the potential bidirectional communication between these systems.

Main Methods:

• In vitro viral infection of lymphocytes to induce peptide synthesis.
• Measurement of immunoreactive ACTH and endorphins.
• In vivo studies in hypophysectomized mice and human subjects.
• Assessment of serum corticosterone and cortisol levels.
• In vitro antibody synthesis assays and receptor binding studies.

Main Results:

• Newcastle disease virus infection induced de novo synthesis of immunoreactive ACTH and endorphins in lymphocytes.
• Lymphocyte ACTH exhibited biological activity in vivo, increasing corticosterone levels in hypophysectomized mice.
• B cell depletion impaired the corticosterone response to viral infection.
• Typhoid vaccine stimulated lymphocyte ACTH production in humans, correlating with cortisol increases.
• Pituitary ACTH and alpha-endorphin demonstrated immunosuppressive effects and bound to lymphocyte receptors.

Conclusions:

• Lymphocytes synthesize bioactive ACTH and endorphins, particularly during viral infections.
• A bidirectional signaling pathway exists between the immune and neuroendocrine systems using shared peptide hormones.
• This cross-talk is mediated by hormones like ACTH and endorphins, and their receptors on lymphocytes.