Self and nonself: duality of immune system

Area of Science:

• Evolutionary biology
• Immunology
• Developmental biology

Background:

• Mammalian immune systems primarily evolved for defense against external pathogens like parasites and microorganisms.
• The evolutionary trajectory from amphibians to mammals resulted in a loss of immune surveillance for oncogenesis (cancer formation).
• A fundamental duality exists between developmental antigens and tumor-specific antigens, defining the targets of immune self-defense mechanisms.

Purpose of the Study:

• To re-evaluate the evolutionary origins and functions of the immune system.
• To explain the duality of self-defense and defense against foreign bodies in the context of immunity.
• To challenge established immunological theories such as clonal deletion and the internal image network hypothesis.

Main Methods:

• Comparative evolutionary analysis of immune system development across species.
• Theoretical examination of immune system function in relation to oncogenesis and development.
• Critique of existing theories on immunocyte differentiation and self-reactivity.

Main Results:

• The immune system's role in surveying somatic cell retrodifferentiation and driving organogenesis is highlighted.
• The evolutionary loss of oncogenesis surveillance in mammals is a key finding.
• Established theories like clonal deletion and the idio-antiidio network model are questioned based on evolutionary and functional perspectives.

Conclusions:

• Mammalian immunity's primary function is defense against external threats, not internal cancer surveillance, due to evolutionary pressures.
• The proposed evolutionary framework reinterprets immune self-reactivity and challenges the teleological significance of clonal deletion.
• Immunity's role in development and retrodifferentiation offers an alternative perspective on its fundamental purpose.