Natural immunity and neuroimmune host defense

Area of Science:

• Immunology
• Neuroendocrinology

Background:

• Innate resistance encompasses non-immune defenses (e.g., bile acids) and natural immunity.
• Natural immunity is mediated by Natural Killer (NK) cells, gamma delta T lymphocytes, and CD5+ B lymphocytes.
• These cells use germ-line receptors recognizing conserved epitopes (homotopes).

Purpose of the Study:

• To elucidate the mechanisms and regulation of innate resistance and natural immunity.
• To understand the role of the neuroendocrine system in modulating immune responses.
• To highlight the importance of natural immunity as a first and last line of defense.

Main Methods:

• Review of existing literature on innate resistance and natural immunity.
• Analysis of the roles of specific immune cells (NK, gamma delta T, CD5+ B) and their receptors.
• Examination of regulatory factors including cytokines, hormones, and acute phase proteins.

Main Results:

• NK cell activity is regulated by cytokines (e.g., IL-2, interferons) and hormones (e.g., prolactin, growth hormone), not typically antigens.
• CD5+ B cells produce natural antibodies (NAbs) that are polyspecific and stimulated by factors like lipopolysaccharide (LPS).
• During acute phase response, adaptive immunity is suppressed while natural immunity is amplified (immunoconversion) via cytokines, neuroendocrine, and metabolic changes.

Conclusions:

• Natural immunity, involving specific cells and natural antibodies, is critical for host defense.
• The neuroendocrine system plays a significant role in promoting natural immune activity.
• Immunoconversion during illness demonstrates the dynamic interplay between immune, neuroendocrine, and metabolic systems for host protection.