Immune System - MCAT Biological and Biochemical Foundations of Living Systems
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The common precursor for all blood and immune cells, including red blood cells and lymphocytes, is found in what part of the body?
The common precursor for all blood and immune cells, including red blood cells and lymphocytes, is found in what part of the body?
All blood cells, including erythrocytes and lymphocytes, come from the same stem cell precursor in the bone marrow. These hematopoietic stem cells give rise to both the myeloid and lymphoid progenitor cells, which are responsible for all blood cells and immune cells. This common precursor spawns cells that then differentiate into the various components of humoral, cell-mediated, and innate immunity.
All blood cells, including erythrocytes and lymphocytes, come from the same stem cell precursor in the bone marrow. These hematopoietic stem cells give rise to both the myeloid and lymphoid progenitor cells, which are responsible for all blood cells and immune cells. This common precursor spawns cells that then differentiate into the various components of humoral, cell-mediated, and innate immunity.
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Which types of leukocytes are granular?
Which types of leukocytes are granular?
The five types of leukocytes are: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Three of these (neutrophils, eosinophils, and basophils) contain granules, tiny sacs containing enzymes which can lyse microorganisms. The other two leukocytes (lymphocytes and monocytes) do not contain these granules.
The five types of leukocytes are: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Three of these (neutrophils, eosinophils, and basophils) contain granules, tiny sacs containing enzymes which can lyse microorganisms. The other two leukocytes (lymphocytes and monocytes) do not contain these granules.
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Which is not a function of B cells?
Which is not a function of B cells?
B cells play numerous integral roles in the immune response against foreign pathogens (viruses, bacteria, and fungi), including forming transient microenvironments called germinal centers, where they produce long-lived plasma cells that are high affinity for specific antigen and memory B cells. They also serve as antigen-presenting cells and producers of cytokines and chemokines; However, B cells are not able to produce extracellular traps, which primarily are composed of DNA and work to trap pathogens. Neutrophils produce extracellular traps.
B cells play numerous integral roles in the immune response against foreign pathogens (viruses, bacteria, and fungi), including forming transient microenvironments called germinal centers, where they produce long-lived plasma cells that are high affinity for specific antigen and memory B cells. They also serve as antigen-presenting cells and producers of cytokines and chemokines; However, B cells are not able to produce extracellular traps, which primarily are composed of DNA and work to trap pathogens. Neutrophils produce extracellular traps.
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Which of the following group of cells are of the myeloid lineage?
Which of the following group of cells are of the myeloid lineage?
Cells of myeloid lineage include dendritic cells, monocytes, macrophages, neutrophils, basophils, and eosinophils, while cells of lymphoid lineage include NK cells, B cells and T cells.
Cells of myeloid lineage include dendritic cells, monocytes, macrophages, neutrophils, basophils, and eosinophils, while cells of lymphoid lineage include NK cells, B cells and T cells.
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Which of the following statements is true?
Which of the following statements is true?
Naive B cells (and most other immune cell subtypes) need more than one signal to become activated. They normally need B cell receptor signaling (signal 1), costimulation by other receptors (signal 2), and cytokines/chemokines (signal 3). This system is necessary in order to prevent aberrant activation of lymphocytes (safeguard against autoimmunity).
In regards to the other statements, there are numerous autoreactive B cells at any given time due to the stochastic nature of VDJ recombination and germinal center reactions. Therefore, tolerance mechanisms and checkpoints are incredibly important to keep these cells in check; central and peripheral tolerance are equally important. Self-nuclear reactive B cells and T cells are both necessary and critical in autoimmune pathogenesis. Female sex hormones are definitely believed to contribute greatly to autoimmune disease pathogenesis (e.g. estrogen). Over 75% of autoimmune patients are women.
Naive B cells (and most other immune cell subtypes) need more than one signal to become activated. They normally need B cell receptor signaling (signal 1), costimulation by other receptors (signal 2), and cytokines/chemokines (signal 3). This system is necessary in order to prevent aberrant activation of lymphocytes (safeguard against autoimmunity).
In regards to the other statements, there are numerous autoreactive B cells at any given time due to the stochastic nature of VDJ recombination and germinal center reactions. Therefore, tolerance mechanisms and checkpoints are incredibly important to keep these cells in check; central and peripheral tolerance are equally important. Self-nuclear reactive B cells and T cells are both necessary and critical in autoimmune pathogenesis. Female sex hormones are definitely believed to contribute greatly to autoimmune disease pathogenesis (e.g. estrogen). Over 75% of autoimmune patients are women.
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Which of the following is not a true statement regarding germinal centers?
Which of the following is not a true statement regarding germinal centers?
T cells, especially CD4+ follicular helper T cells, are absolutely critical and necessary for the induction and maintenance of germinal centers.
T cells, especially CD4+ follicular helper T cells, are absolutely critical and necessary for the induction and maintenance of germinal centers.
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Which cytokine is typically associated with the T helper 1 (Th1) response?
Which cytokine is typically associated with the T helper 1 (Th1) response?
The following helper T cells are paired with the following cytokines:
Th1 - IFN-gamma
Th2 - IL-4
Th9 - IL-9
Th17 - IL-17
Tfh - IL-21
The following helper T cells are paired with the following cytokines:
Th1 - IFN-gamma
Th2 - IL-4
Th9 - IL-9
Th17 - IL-17
Tfh - IL-21
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What is the group of diseases called when a person's immune system loses its ability to recognize its own MHC proteins?
What is the group of diseases called when a person's immune system loses its ability to recognize its own MHC proteins?
Autoimmunity arises when one's immune system is unable to recognize its own MHC proteins, which could potentially lead to aberrant activation of the immune response. Furthermore, autoreactive immune cells that are normally induced to undergo apoptosis may be able to escape these tolerance mechanisms and induce tissue damage.
Autoimmunity arises when one's immune system is unable to recognize its own MHC proteins, which could potentially lead to aberrant activation of the immune response. Furthermore, autoreactive immune cells that are normally induced to undergo apoptosis may be able to escape these tolerance mechanisms and induce tissue damage.
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Which of the following class of immunoglobulins is normally responsible for the promotion of the allergy response?
Which of the following class of immunoglobulins is normally responsible for the promotion of the allergy response?
IgE plays a critical role in induction and promotion of type I hypersensitivity (allergy, asthma, etc.) normally through engagement of Fc receptors on the surface of basophils and mast cells, which primes them to produce large quantities of granules and chemical mediators (including histamines and cytokines).
IgE plays a critical role in induction and promotion of type I hypersensitivity (allergy, asthma, etc.) normally through engagement of Fc receptors on the surface of basophils and mast cells, which primes them to produce large quantities of granules and chemical mediators (including histamines and cytokines).
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Which of the following cell types is considered to be part of the innate immune response?
Which of the following cell types is considered to be part of the innate immune response?
Natural killer (NK) cells are prominent members of the initial innate immune response against foreign pathogens. They play numerous integral roles in the innate response including cytotoxic killing, cytokine production, and antibody-mediated cell cytotoxicity.
Natural killer (NK) cells are prominent members of the initial innate immune response against foreign pathogens. They play numerous integral roles in the innate response including cytotoxic killing, cytokine production, and antibody-mediated cell cytotoxicity.
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Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the loss of tolerance to self antigens leading to the presence of high autoantibody titers. There are several underlying causes behind SLE, one of which is a dysregulation in the clearance of apoptotic cells, which can lead to secondary necrosis. This leads to the leakage of danger signals which contributes to the loss of peripheral tolerance and chronic inflammation.
A deficiency in the clearance of apoptotic cells can be attributed to which immune cell type?
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the loss of tolerance to self antigens leading to the presence of high autoantibody titers. There are several underlying causes behind SLE, one of which is a dysregulation in the clearance of apoptotic cells, which can lead to secondary necrosis. This leads to the leakage of danger signals which contributes to the loss of peripheral tolerance and chronic inflammation.
A deficiency in the clearance of apoptotic cells can be attributed to which immune cell type?
The defect in clearance of apoptotic cells in SLE is mainly attributed to macrophages, which serve integral roles in phagocytosis of dead cells and debris. An inability to clear these apoptotic cells over time leads to secondary necrosis, which results in the production and release of several DAMPS or damage-associated molecular pattern molecules which are potent inducers of the immune response.
The defect in clearance of apoptotic cells in SLE is mainly attributed to macrophages, which serve integral roles in phagocytosis of dead cells and debris. An inability to clear these apoptotic cells over time leads to secondary necrosis, which results in the production and release of several DAMPS or damage-associated molecular pattern molecules which are potent inducers of the immune response.
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Somatic hypermutation of B cell receptor (BCR) genes in immature, developing B lymphocytes generates numerous specificities that are useful against a specific foreign antigen, however the process generates many more specificities that are either low affinity or reactive against self-antigens. Tolerance mechanisms, which include apoptosis or anergy, are in place in the bone marrow to prevent these "non-useful" or "harmful" B cells from exiting. However, these checkpoints are not 100% accurate and numerous B cells with autoreactive BCR's leave and travel to secondary lymphoid tissues.
Tolerance checkpoints exist in secondary lymphoid tissues to purge the repertoire of low-affinity or autoreactive B cells. What is the tolerance checkpoint mechanism in the secondary lymphoid tissues referred to as?
Somatic hypermutation of B cell receptor (BCR) genes in immature, developing B lymphocytes generates numerous specificities that are useful against a specific foreign antigen, however the process generates many more specificities that are either low affinity or reactive against self-antigens. Tolerance mechanisms, which include apoptosis or anergy, are in place in the bone marrow to prevent these "non-useful" or "harmful" B cells from exiting. However, these checkpoints are not 100% accurate and numerous B cells with autoreactive BCR's leave and travel to secondary lymphoid tissues.
Tolerance checkpoints exist in secondary lymphoid tissues to purge the repertoire of low-affinity or autoreactive B cells. What is the tolerance checkpoint mechanism in the secondary lymphoid tissues referred to as?
Peripheral tolerance is the correct term for the tolerance checkpoint mechanisms that are instituted in the secondary lymphoid organs such as spleen and lymph nodes. B cells with BCR specificities that are low affinity or reactive against self-nuclear antigen will be purged from the repertoire.
Peripheral tolerance is the correct term for the tolerance checkpoint mechanisms that are instituted in the secondary lymphoid organs such as spleen and lymph nodes. B cells with BCR specificities that are low affinity or reactive against self-nuclear antigen will be purged from the repertoire.
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Bone marrow chimeric mice are an invaluable tool used by immunologists to elucidate specific mechanisms of the immune response. The generation of these chimeras involve whole body irradiation to eliminate the mouse bone marrow followed by adoptive transfer of bone marrow from a donor mouse (usually transgenic).
One critical step in the successful generation of bone marrow chimeric mice involves the depletion of T cells from the donor bone marrow. Which of the following is reason for this necessary step?
Bone marrow chimeric mice are an invaluable tool used by immunologists to elucidate specific mechanisms of the immune response. The generation of these chimeras involve whole body irradiation to eliminate the mouse bone marrow followed by adoptive transfer of bone marrow from a donor mouse (usually transgenic).
One critical step in the successful generation of bone marrow chimeric mice involves the depletion of T cells from the donor bone marrow. Which of the following is reason for this necessary step?
T cells from the donor must be depleted due to the risk of incompatible MHC antigens on the recipient cells. If there is incompatibility, the donor T cells will attack and kill the host cells resulting in a graft versus host response.
T cells from the donor must be depleted due to the risk of incompatible MHC antigens on the recipient cells. If there is incompatibility, the donor T cells will attack and kill the host cells resulting in a graft versus host response.
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Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.
In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.
Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.
What is the best characterization of the immune response described in the passage?
Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.
In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.
Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.
What is the best characterization of the immune response described in the passage?
The initial response is an effort to repair physical damage, while the chronic response involves the recognition of antigens. Innate immunity refers to the body's natural untargeted defenses, such as the cells that would work to repair damage. Adaptive immunity is targeted to specific pathogens via antigen presentation. Thus, the pattern described in the passage is initially innate immunity, then adaptive immunity.
The initial response is an effort to repair physical damage, while the chronic response involves the recognition of antigens. Innate immunity refers to the body's natural untargeted defenses, such as the cells that would work to repair damage. Adaptive immunity is targeted to specific pathogens via antigen presentation. Thus, the pattern described in the passage is initially innate immunity, then adaptive immunity.
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Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the loss of tolerance to self antigens leading to the presence of high autoantibody titers. Dysregulated peripheral tolerance and hyperactive germinal centers have been proposed to be one of the driving forces behind the accumulation of high autoantibodies.
What immune cell type is the product of germinal centers and most likely the cell mediating the production of autoantibodies?
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the loss of tolerance to self antigens leading to the presence of high autoantibody titers. Dysregulated peripheral tolerance and hyperactive germinal centers have been proposed to be one of the driving forces behind the accumulation of high autoantibodies.
What immune cell type is the product of germinal centers and most likely the cell mediating the production of autoantibodies?
Plasma cells are the main product of germinal centers and are potent antibody factories. Dysregulated peripheral tolerance and germinal centers can lead to the production of plasma cells that are reactive towards self-nuclear antigens.
Plasma cells are the main product of germinal centers and are potent antibody factories. Dysregulated peripheral tolerance and germinal centers can lead to the production of plasma cells that are reactive towards self-nuclear antigens.
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Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.
In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.
Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.
Which compound is most likely responsible for initiating the inflammation response that results from the autoimmune attack?
Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.
In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.
Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.
Which compound is most likely responsible for initiating the inflammation response that results from the autoimmune attack?
Fibrin and fibrinogen are involved in wound healing and scab formation. Dopamine is a neurotransmitter in the brain. Fibrogen is not a real protein at all.
Histamine is the primary inflammatory molecule in the body and is released from mast cells during an immune response or trauma.
Fibrin and fibrinogen are involved in wound healing and scab formation. Dopamine is a neurotransmitter in the brain. Fibrogen is not a real protein at all.
Histamine is the primary inflammatory molecule in the body and is released from mast cells during an immune response or trauma.
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Which of the following correctly matches the type of immunity to the way it was recieved?
Which of the following correctly matches the type of immunity to the way it was recieved?
Active immunity is when you are exposed to a pathogen, either through vaccination, another person with the disease, or any other means, and your body responds by producing specific antibodies with B-cells to destroy the pathogen. Passive immunity is acquired from antibody transfer, so the body does not produce its own antibodies.
Active immunity is when you are exposed to a pathogen, either through vaccination, another person with the disease, or any other means, and your body responds by producing specific antibodies with B-cells to destroy the pathogen. Passive immunity is acquired from antibody transfer, so the body does not produce its own antibodies.
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Which of these choices is not a function of T-cells?
Which of these choices is not a function of T-cells?
The only choice that is not a function of any type of T-cell is the direct production of antibodies (which is performed by B-cells). Cytotoxic T-cells kill other cells that are bound to antigen/MHC-I complexes. Suppressor T-cells tone down the response of both B- and T-cells, and helper T-cells secrete cytokines, which increase the activity of many other immune cell types.
The only choice that is not a function of any type of T-cell is the direct production of antibodies (which is performed by B-cells). Cytotoxic T-cells kill other cells that are bound to antigen/MHC-I complexes. Suppressor T-cells tone down the response of both B- and T-cells, and helper T-cells secrete cytokines, which increase the activity of many other immune cell types.
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Sexually transmitted diseases are a common problem among young people in the United States. One of the more common diseases is caused by the bacterium Neisseria gonorrhoeae, which leads to inflammation and purulent discharge in the male and female reproductive tracts.
The bacterium has a number of systems to evade host defenses. Upon infection, it uses pili to adhere to host epithelium. The bacterium also uses an enzyme, gonococcal sialyltransferase, to transfer a sialyic acid residue to a gonococcal surface lipooligosaccharide (LOS). A depiction of this can be seen in Figure 1. The sialyic acid residue mimics the protective capsule found on other bacterial species.
Once infection is established, Neisseria preferentially infects columnar epithelial cells in the female reproductive tract, and leads to a loss of cilia on these cells. Damage to the reproductive tract can result in pelvic inflammatory disease, which can complicate pregnancies later in the life of the woman.
The first line of defense by a human host against a potential Neisseria infection is which of the following?
Sexually transmitted diseases are a common problem among young people in the United States. One of the more common diseases is caused by the bacterium Neisseria gonorrhoeae, which leads to inflammation and purulent discharge in the male and female reproductive tracts.
The bacterium has a number of systems to evade host defenses. Upon infection, it uses pili to adhere to host epithelium. The bacterium also uses an enzyme, gonococcal sialyltransferase, to transfer a sialyic acid residue to a gonococcal surface lipooligosaccharide (LOS). A depiction of this can be seen in Figure 1. The sialyic acid residue mimics the protective capsule found on other bacterial species.
Once infection is established, Neisseria preferentially infects columnar epithelial cells in the female reproductive tract, and leads to a loss of cilia on these cells. Damage to the reproductive tract can result in pelvic inflammatory disease, which can complicate pregnancies later in the life of the woman.
The first line of defense by a human host against a potential Neisseria infection is which of the following?
Innate defenses, such as the skin or macrophages, are the first line of defense against infection. Other responses only become effective if a pathogen cannot be repelled by innate mechanisms.
Innate defenses, such as the skin or macrophages, are the first line of defense against infection. Other responses only become effective if a pathogen cannot be repelled by innate mechanisms.
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Cryptosporidium is a genus of gastrointestinal parasite that infects the intestinal epithelium of mammals. Cryptosporidium is water-borne, and is an apicomplexan parasite. This phylum also includes Plasmodium, Babesia, and Toxoplasma.
Apicomplexans are unique due to their apicoplast, an apical organelle that helps penetrate mammalian epithelium. In the case of cryptosporidium, there is an interaction between the surface proteins of mammalian epithelial tissue and those of the apical portion of the cryptosporidium infective stage, or oocyst. A scientist is conducting an experiment to test the hypothesis that the oocyst secretes a peptide compound that neutralizes intestinal defense cells. These defense cells are resident in the intestinal epithelium, and defend the tissue by phagocytizing the oocysts.
She sets up the following experiment:
As the neutralizing compound was believed to be secreted by the oocyst, the scientist collected oocysts onto growth media. The oocysts were grown among intestinal epithelial cells, and then the media was collected. The media was then added to another plate where Toxoplasma gondii was growing with intestinal epithelial cells. A second plate of Toxoplasma gondii was grown with the same type of intestinal epithelium, but no oocyst-sourced media was added.
A patient is hiking through Nepal and comes down with a case of diarrhea caused by cryptosporidium. You determine that his body was fighting this infection mainly by mounting an antibody response. Where do the cells most directly responsible for this response develop?
Cryptosporidium is a genus of gastrointestinal parasite that infects the intestinal epithelium of mammals. Cryptosporidium is water-borne, and is an apicomplexan parasite. This phylum also includes Plasmodium, Babesia, and Toxoplasma.
Apicomplexans are unique due to their apicoplast, an apical organelle that helps penetrate mammalian epithelium. In the case of cryptosporidium, there is an interaction between the surface proteins of mammalian epithelial tissue and those of the apical portion of the cryptosporidium infective stage, or oocyst. A scientist is conducting an experiment to test the hypothesis that the oocyst secretes a peptide compound that neutralizes intestinal defense cells. These defense cells are resident in the intestinal epithelium, and defend the tissue by phagocytizing the oocysts.
She sets up the following experiment:
As the neutralizing compound was believed to be secreted by the oocyst, the scientist collected oocysts onto growth media. The oocysts were grown among intestinal epithelial cells, and then the media was collected. The media was then added to another plate where Toxoplasma gondii was growing with intestinal epithelial cells. A second plate of Toxoplasma gondii was grown with the same type of intestinal epithelium, but no oocyst-sourced media was added.
A patient is hiking through Nepal and comes down with a case of diarrhea caused by cryptosporidium. You determine that his body was fighting this infection mainly by mounting an antibody response. Where do the cells most directly responsible for this response develop?
Antibodies are produced by B-cells, which develop in the bone marrow. T-cells develop in the thymus.
You can remember B for bone marrow, T for thymus.
Antibodies are produced by B-cells, which develop in the bone marrow. T-cells develop in the thymus.
You can remember B for bone marrow, T for thymus.
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