RISH. VI: General evolutionary aspects of the immune system.

Area of Science:

• Evolutionary cell biology
• Molecular evolution
• Immunology

Background:

• Eukaryotic plasma membranes evolved flexibility by delegating functions to organelles.
• Early cell speciation occurred due to plasma membrane variations.
• Sexual reproduction necessitated like-cell recognition, initially intracellular in protozoa.

Purpose of the Study:

• To trace the evolutionary origins of cell-surface recognition mechanisms.
• To explain the transition of alloincompatibility expression from intracellular to cell-surface.
• To elucidate the role of lectins in cell identification, feeding, and immune responses.

Main Methods:

• Comparative analysis of prokaryotic and eukaryotic cell membrane evolution.
• Tracing the role of RNA-templated DNA synthesis in inheritable lectin expression.
• Examining the functional shift of lectins from feeding to cell-cell recognition.

Main Results:

• Plasma membrane alloincompatibility shifted to cell-surface expression with Metazoa evolution.
• Cell-surface lectins, induced by complementary RNA, facilitated like-cell identification.
• Inheritable lectins, expressed intra- and extracellularly, played roles in feeding and alloincompatibility.

Conclusions:

• Cell-surface lectins are crucial for like-cell identification in Metazoa, forming the basis of histocompatibility antigens.
• Evolutionary pressures transformed primitive feeding lectins into key components for differentiation and immunological reactions.
• The study highlights the deep evolutionary roots of cellular recognition and immune system components.