Milk allergy and intolerance
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Milk allergy and intolerance
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[ID] => 554843
[post_author] => 12815
[post_date] => 2024-12-23 18:33:54
[post_date_gmt] => 2024-12-23 23:33:54
[post_content] => Practice Passage (Question 1-6)
*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
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
[post_title] => Milk allergy and intolerance
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[question] => What is the difference between milk allergy and milk intolerance?
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[answer] => 4
[description] => Reason for Correct Answer:
The passage states that milk intolerance is caused by a “deficiency of enzymes needed for proper digestion.” Lactose is the main sugar found in milk.
Accordingly, a deficiency of lactase (the enzyme that breaks down lactose) often results in milk intolerance.
Figure 1a shows that the presence of protein Bos d 5 only affects the CD4+ cell response. (In the CD8+ response, the graphs are all the same, regardless of the presence of the Bos d 5 protein.)
Therefore, the CD4+ cellular response is likely responsible for milk allergy.
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[answers] => Array
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[0] => Array
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[each_answer] => A. Intolerance is when CD4+ cells respond to milk; allergy is when individuals lack lactase.
)
[1] => Array
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[each_answer] => B. Intolerance is when CD8+ cells respond to milk; allergy is when individuals lack lactase.
)
[2] => Array
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[each_answer] => C. Allergy is when CD8+ cells respond to milk; intolerance is when individuals lack lactase.
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[3] => Array
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[each_answer] => D. Allergy is when CD4+ cells respond to milk; intolerance is when individuals lack lactase.
)
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[1] => Array
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[quiz_unique_key] => 1403770772
[question] => What can researchers conclude about the effect of different forms of Bos d 5 on specific T-cell subpopulations?
[value] => Array
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[answer] => 1
[description] => Reason for Correct Answer:
Cell differentiation factors 4 and 8 are typical of helper and cytotoxic T cells, respectively.
Only CD4+ cells showed a differential activation rate.
Only apo-Bos d5 increased the number of CD4+ cells, compared to treatment with PMA alone.
Thus, apo-Bos d5 causes a reaction in helper T cells.
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[answers] => Array
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[0] => Array
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[each_answer] => A. Apo-Bos d 5 causes a reaction in helper T-cells
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[1] => Array
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[each_answer] => B. Apo-Bos d 5 causes a reaction in cytotoxic T-cells
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[2] => Array
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[each_answer] => C. Holo-Bos d 5 causes a reaction in helper T-cells
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[each_answer] => D. Holo-Bos d 5 causes a reaction in cytotoxic T-cells
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[2] => Array
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[quiz_unique_key] => 1403770772
[question] => The results of the study support the likelihood of involvement of which type of immunity in milk allergy?
[value] => Array
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[answer] => 1
[description] => Reason for Correct Answer:
CD4+ T cells, also known as helper T cells, are a central component of the adaptive immune system. They can interact with both B cells and other immune cells, such as CD8+ T cells (cytotoxic T cells) and macrophages, to initiate and regulate immune reactions.
CD4+ T cells can interact with B cells and provide essential signals for antibody production, which is characteristic of humoral immunity. CD4+ T cells are also involved in cell-mediated immune responses, which are critical in recognizing and responding to infected or abnormal cells, because they play a role in activating CD8+ T cells.
CD8 T cells, also known as cytotoxic T cells, are a type of immune cell that plays a central role in cell-mediated immunity. They are crucial for identifying and destroying cells that have been infected by viruses, bacteria, or other intracellular pathogens.
The activation of CD4+ T cells but NOT CD8+ T cells in response to milk proteins suggests that humoral immunity is likely involved in mediating milk allergies.
In the context of milk allergies, CD4+ T cells assist B cells in making antibodies that bind to milk proteins, leading to the activation of various immune effector mechanisms and the initiation of the humoral immune response.
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[answers] => Array
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[0] => Array
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[each_answer] => A. Humoral immunity
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[each_answer] => B. Cell-mediated immunity
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[2] => Array
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[each_answer] => C. Innate immunity
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[each_answer] => D. Autoimmunity
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[3] => Array
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[quiz_unique_key] => 1403770772
[question] => In the case of milk allergies, which compound is the antigen and which compound is the epitope?
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[answer] => 3
[description] => Reason for Correct Answer:
Antigens are any substance that provokes an immune reaction.
Epitopes, also known as antigen determinants, are specific parts of antigens that are recognized by immune cells.
The experiment shows that Bos d 5 has an antigenic function, but only when the epitope siderophore is not bound with iron, thus Bos D 5 and siderophore lacking iron are the antigen and epitope, respectively.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. Siderophore is the antigen and holo-Bos D 5 is the epitope.
)
[1] => Array
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[each_answer] => B. Siderophore is the antigen and apo-Bos D 5 is the epitope.
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[2] => Array
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[each_answer] => C. Bos D 5 is the antigen and siderophore lacking iron is the epitope.
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[each_answer] => D. Bos D 5 is the antigen and siderophore loaded with iron is the epitope.
)
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[quiz_unique_key] => 1403770772
[question] => The action of which immunoglobulin would result in the immediate formation of hives following milk protein ingestion?
[value] => Array
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[answer] => 2
[description] => Reason for Correct Answer:
Hives, also known as urticaria, are a common allergic skin reaction characterized by red, itchy welts or raised bumps on the skin.
Different antibodies, or immunoglobulins, mediate different immune processes.
Here is a summary of the immunoglobulins:
- IgA: Predominantly found in mucosal surfaces and body secretions, providing defense against pathogens at mucosal entry points.
- IgG: The most abundant antibody in the bloodstream, involved in long-term immune memory and protecting against a wide range of infections.
- IgM: The first antibody produced in response to an infection, effective in agglutinating pathogens and initiating the complement system.
- IgD: Present on the surface of B cells, its exact function is still not fully understood, but it may play a role in B cell activation and immune signaling.
- IgE: Involved in immediate hypersensitivity reactions, such as allergies, by triggering mast cell and basophil activation leading to the release of inflammatory mediators.
IgE is the antibody that is responsible for immediate allergic and hypersensitivity reactions, such as hives.
In the context of allergies like milk allergies, CD4 cells release signaling molecules (cytokines) that stimulate B cells to produce specific antibodies called immunoglobulin E (IgE). These IgE antibodies then bind to mast cells and basophils, which are types of immune cells. When the person encounters the allergen again, it binds to the IgE antibodies on the surface of these cells, triggering the release of inflammatory substances, such as histamine, which contribute to the allergic response
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[answers] => Array
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[each_answer] => A. IgA
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[each_answer] => B. IgE
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[each_answer] => C. IgG
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[each_answer] => D. IgM
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[quiz_unique_key] => 1997864699
[question] => What is the most likely side effect of milk intolerance?
[value] => Array
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[answer] => 1
[description] => Reason for Correct Answer:
Milk intolerance is caused by the deficiency of the enzyme lactase, which is responsible for breaking down lactose, the sugar found in milk.
Without sufficient lactase, lactose remains undigested and reaches the large intestine, which causes an increase in osmotic pressure in the intestines.
This osmotic effect occurs in the lumen of the intestines and results in water being drawn into the lumen, which causes diarrhea.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. Diarrhea due to increased osmotic pressure in the lumen of the intestines
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[each_answer] => B. Constipation due to increased osmotic pressure in the intestinal epithelium
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[2] => Array
(
[each_answer] => C. Antibody-mediated respiratory systems, such as wheezing and coughing
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[3] => Array
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[each_answer] => D. Weakness and pain from cross-reactivity with muscle proteins
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Figure 1
