MCAT Biology : Systems Biology and Tissue Types
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Example Question #401 : Systems Biology And Tissue Types
Cholera is a disease caused by vibrio cholerae, a bacteria which enters the body through the digestive tract. The bacteria is absorbed by the small intestine and enters the blood stream. Which of the following antibodies would be most effective at preventing cholera?
IgD
IgE
IgA
IgM
IgG
IgA
Because V. cholerae enters the body through the digestive tract, the best antibody that can prevent infection would be one that is secreted into the small intestine. IgA is a secretory antibody that can be secreted by the cells lining the small intestine, into the small intestine lumen.
The other antibodies (IgG, IgM, IgD, and IgE) cannot be secreted out of the body and would only be effective once the V. cholerae has entered the body; therefore, IgA is the correct answer.
Example Question #1 : Antibodies And Antigens
A patient is admitted to the hospital needing a blood transfusion. The patient has type A negative blood. Which of the following is true?
Both of the patient's parents must have type A blood
The patient can receive AB blood
The patient can receive O negative blood
The patient creates A antibodies
The patient can receive O negative blood
When looking at blood types, remember that the allele for blood type represents the type of antigen presented on the person's red blood cells. The positive or negative sign is indicative of whether or not the person makes Rh factors. If a person is negative, they create antibodies to positive Rh factors. If a person is missing an allele in their blood type, they will make antibodies for that particular antigen.
The patient in question will have antigens for type A, and antibodies against type B and Rh factor.
Type O negative blood means that there are no antigens on the red blood cells, meaning that a person with type A negative blood can receive type O negative blood. O negative blood is widely considered the "universal donor" type because it lacks any antigens that may react with antibodies in a recipient's blood. We cannot draw conclusions about the patient's parents; we know that one parent carried the A allele, but they could have been AB and the second parent could have been type O.
Example Question #1 : Antibodies And Antigens
Which part of the antibody recognizes the antigen?
The variable regions of the light chains
The variable regions of the heavy and light chain
The constant regions of the heavy and light chain
The variable and constant regions of the heavy chains
The variable regions of the heavy and light chain
The antibody has two light chains and two heavy chains, each with a constant and a variable region. The variable regions of each chain are randomized during cell proliferation and recognize different antigens. This provides diversity of recognition for a better immune system.
Example Question #62 : Immune System
Type 1 diabetes is a well-understood autoimmune disease. Autoimmune diseases result from an immune system-mediated attack on one’s own body tissues. In normal development, an organ called the thymus introduces immune cells to the body’s normal proteins. This process is called negative selection, as those immune cells that recognize normal proteins are deleted. If cells evade this process, those that recognize normal proteins enter into circulation, where they can attack body tissues. The thymus is also important for activating T-cells that recognize foreign proteins.
As the figure below shows, immune cells typically originate in the bone marrow. Some immune cells, called T-cells, then go to the thymus for negative selection. Those that survive negative selection, enter into general circulation to fight infection. Other cells, called B-cells, directly enter general circulation from the bone marrow. It is a breakdown in this carefully orchestrated process that leads to autoimmune disease, such as type 1 diabetes.
There are many ways that the body's immune system can attack its own tissues in autoimmune disease. A scientist discovers that in type 1 diabetes, antibodies play a key role in attracting lymphocytes to normal tissue, which is then damaged or destroyed. What kinds of cells typically produce antibodies?
I. T-cells
II. B-cells
III. Macrophages
I, only
II and III
III, only
I and II
II, only
II, only
B-cells are the only cells to produce antibodies, which then target pathogens (or normal tissue, in autoimmune disease) for phagocytosis or cell-killing via other immune pathways. T-cells mediate the adaptive immune response and activation of B-cells, but do not produce antibodies. Macrophages help to phagocytose foreign particulates and pathogens, and can react to the antigens or antibodies attached to a foreign pathogen, but do not produce antibodies.
Example Question #1 : Antibodies And Antigens
Which of the following cell types secretes antibodies?
T-cells
Natural killer cells
Neutrophils
B-cells
Macrophages
B-cells
B-cells are responsible for the humoral immune response, which is the production of antibodies in response to a specific antigen. T-cells mediate the adaptive immune response by helping to activate B-cells (helper T-cells) and attacking foreign pathogens (cytotoxic T-cells). Natural killer cells are part of the innate immune response, and kill infected or damaged cells. Macrophages and neutrophils are phagocytes and help to attack and digest pathogens.
Example Question #91 : Immune And Lymphatic Systems
Major histocompatibility complex (MHC) I molecules primarily display antigens derived from what type of pathogen?
Bacteria
Viruses
Fungi
Parasites
Viruses
The "self" antigens that prevent T-cells from attacking the body are called MHC molecules. These molecules come in two classes: class I and class II. RNA, DNA, and proteins in viruses are displayed after the virus is ingested by an antigen-presenting cell using MHC class I molecules. The antigen-presenting cell reports the MHC molecule corresponding to the virus to a helper T-cells. Once the helper T-cells see this unrecognized part of the virus, and detect it as different from "self," they can initiate the adaptive immune response.
Example Question #11 : Antibodies And Antigens
Major histocompatibility complex (MHC) II molecules are responsible for displaying antigens from what invading pathogen?
Viruses
Parasites
Fungi
Bacteria
Bacteria
The "self" antigens that prevent T-cells from attacking the body are called MHC molecules. These molecules come in two classes: class I and class II. RNA, DNA, and proteins from bacteria are displayed after the bacterium is ingested by an antigen-presenting cell using MHC class II molecules. The antigen-presenting cell reports the MHC molecule corresponding to the bacteria to a helper T-cells. Once the helper T-cells see this unrecognized part of the bacterium, and detect it as different from "self," they can initiate the adaptive immune response.
Example Question #63 : Immune System
Blood types are designated A, B, AB, and O depending on the glycoprotein presented on the surface of the red blood cells. If a person has glycoproteins 
AB
O
B
A
A
The glycoproteins 
Example Question #11 : Antibodies And Antigens
Hypersensitivity reactions occur when body tissues are affected by an abnormal immune reaction. The result is damage to normal tissues and clinical illness. A peanut allergy is an example of a hypersensitivity reaction, but there are three additional broad classes.
One class involves the abnormal production or deposition of antibodies. Antibodies are B-cell derived molecules that normally adhere to pathogens, rendering them unable to continue an infection. When antibodies are produced against normal tissues, however, disease can result. Figure 1 depicts a schematic structure of an antibody.
Antibodies can be divided into two peptide chains: heavy and light. Heavy chains form the backbone of the antibody, and are attached to light chains via covalent bonding. Each heavy and light chain is then further divided into constant and variable regions. Variable regions exhibit molecular variety, generating a unique chemical identity for each antibody. These unique patterns help guarantee that the body can produce antibodies to recognize many possible molecular patterns on invading pathogens.
Before antibodies enter into circulation, they exist as B-cell receptors (BCRs). BCRs are transmembrane proteins that are identical to the antibodies that exist in free circulation, with the exception of one component. Which component is likely present in BCRs, but not in antibodies in solution with blood?
A span of charged amino acids
A span of hydrophilic amino acids
A span of hydrophobic amino acids
A span of basic amino acids
A span of acidic amino acids
A span of hydrophobic amino acids
A B-cell receptor (BCR) is a transmembrane protein, and thus must have an integral membrane domain consisting of hydrophobic amino acids. This is different from antibodies in solution, which would likely not have such an integral membrane domain. The mature antibody must be capable of being in the aqueous blood solution. The persistence of a hydrophobic region in the antibody would inhibit its solubility in the blood, reducing its functionality.
Example Question #401 : Systems Biology And Tissue Types
Hypersensitivity reactions occur when body tissues are affected by an abnormal immune reaction. The result is damage to normal tissues and clinical illness. A peanut allergy is an example of a hypersensitivity reaction, but there are three additional broad classes.
One class involves the abnormal production or deposition of antibodies. Antibodies are B-cell derived molecules that normally adhere to pathogens, rendering them unable to continue an infection. When antibodies are produced against normal tissues, however, disease can result. Figure 1 depicts a schematic structure of an antibody.
Antibodies can be divided into two peptide chains: heavy and light. Heavy chains form the backbone of the antibody, and are attached to light chains via covalent bonding. Each heavy and light chain is then further divided into constant and variable regions. Variable regions exhibit molecular variety, generating a unique chemical identity for each antibody. These unique patterns help guarantee that the body can produce antibodies to recognize many possible molecular patterns on invading pathogens.
A patient presents to their local primary care clinic with a 1-day old influenza infection. Their blood is drawn and analyzed for antibodies. Four months after the infection, their physician draws their blood again and studies the presence of antibodies. Which of the following is most likely to be true?
There will be fewer anti-influenza antibodies at the four month blood draw
Antibodies do not form in response to viral infections such as influenza
There will be an equal number of anti-influenza antibodies at the four month blood draw and the initial draw
We cannot predict the changes in the amount of antibodies at the four month blood draw relative to the initial draw
There will be more anti-influenza antibodies at the four month blood draw
There will be more anti-influenza antibodies at the four month blood draw
Antibodies are part of the adaptive immune response. As a result, we would expect that their concentration during an acute infection would be lower than their concentration in a post-infection (convalescent) serum sample. In fact, many diagnostic assays use this phenomenon to confirm diagnoses.
Antibodies are among the major immune responses to viral infections, especially influenza.
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