Intestinal bacteria play a crucial role as the environmental stimulus for the development of 'naturally occurring' anti-A and anti-B antibodies. Humans are colonized shortly after birth by a vast community of bacteria in the gut. Many of these bacteria, such as Escherichia coli, have polysaccharides (sugars) on their surfaces that are structurally identical or very similar to the A and B blood group antigens. An infant whose red cells lack, for example, the B antigen will be exposed to these B-like bacterial substances. Their developing immune system recognizes these as foreign and produces IgM antibodies against them. These antibodies happen to cross-react with human B antigens. Thus, by around 3-6 months of age, the infant will have a measurable level of anti-B antibodies in their serum, without ever having been exposed to human B-positive red cells.

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Zambia

• Joseph Soko – 101 pts

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