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Course: MCAT > Unit 2

Lesson 3: Foundation 3: Organ Systems

Immune system: Milk allergy and intolerance


Milk intolerance and milk allergy are two distinct conditions with different underlying mechanisms and symptoms. Milk intolerance is primarily caused by the inability to properly digest components of milk, usually due to a deficiency of enzymes needed for proper digestion. Milk allergy, on the other hand, is an immune response to proteins found in milk.
Among the proteins found in milk, the beta-lactoglobulin protein (Bos d 5) is known to help activate T-lymphocytes. Bos d 5 belongs to the lipocalin family, a group of proteins with molecular pockets called siderophores. The siderophores of Bos d 5 can bind to iron, such that Bos d 5 can be found in two forms: an “apo” state (when the siderophore is not bound to iron) and the “holo” state (when the siderophore is bound to iron). The following experiment was designed to investigate the immune-modulatory properties of Bos d 5 in either form.
White blood cells isolated from 25 patients were exposed to phorbol 12-myristate 13-acetate (PMA), a compound that assists in T cell activation, in the presence or absence of the two forms of Bos d 5. Subsequently, changes in the numbers of CD3+CD4+ and CD3+CD8+ cells were measured. The results are shown in Figure 1.
Figure 1 Percentage of activated CD3+CD4+ cells and CD3+CD8+ cells after exposure to PMA, PMA plus apo-Bos d 5, and/or holo-Bos d 5; bars indicate statistical comparison; statistical significance is indicated as follows: = P<0.01, ** = P<0.0001
What is the difference between milk allergy and milk intolerance?
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