ABO antigens are not proteins, but complex carbohydrate chains (oligosaccharides) that are attached to glycoproteins and glycolipids on the surface of red blood cells. The specific A or B determinant is a terminal sugar added to a common precursor chain (the H antigen). The A allele codes for an enzyme (glycosyltransferase) that adds N-acetylgalactosamine. The B allele codes for an enzyme that adds D-galactose. The O allele codes for a non-functional enzyme, so no terminal sugar is added, leaving the H antigen intact. This carbohydrate structure explains why they are not dependent on the cell's DNA for direct synthesis after the cell matures and why they are such potent activators of the innate immune system (through carbohydrate-recognizing antibodies like IgM).

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Zambia

• Naomi Miselo – 31 pts

• Visual Pathway Lesions
• Positive and Negative Symptoms
• Hallucinations and Delusions
• Antipsychotic Medications
• Emergency: Environmental Emergencies