Fill-In-The-Blank: these statements are conceptual; as such there may be other correct answers in addition to the ones provided.
Every lymphocyte in our body has surface receptors that see foreign .
Lymphocytes that mistakenly see "self" antigens undergo programmed cell death a.k.a. . This process occurs in the for T-cells, and the for B-cells.
T-cells have T-cell receptors that see antigens bound to molecules.
The type of MHC molecule found on all cells in our body are called ; those that are only found on phagocytes are called .
Phagocytes can present peptides to T-cells and are consequently called .
T-cells that see foreign peptides on class-I MHC are called T-cells; They express the surface marker .
T-cells that see foreign peptides on class-II MHC are called T-cells; They express the surface marker .
The lymphocyte primarily responsible for killing pathogen-infected cells is the .
Unlike the T-cell receptor, the B-cell receptor can be secreted in serum as .
The 4 major types of immunoglobulin are: , , , and .
The first antibody produced in an immune response is the low-affinity isotype.
is found in tissues and blood, whereas IgM is primarily found just in blood.
is secreted and found on surfaces.
is bound to receptors on mast cells and reacts with and .
Class switching from IgM to IgG/A/E is promoted by cells.
Random mutations in the B-cell receptor antigen binding site can lead to the development of antibodies with much higher binding affinity. This process is called .
Antibodies perform multiple functions including , , , , antibody-dependent cell-mediated cytotoxicity (ADCC) by cells, and mast cell .
are primarily responsible for taking peptide antigens to lymph nodes.
After an infection, some lymphocytes remain as cells.
Multiple Choice Questions:
1) Some non-lymphoid tumor cells (e.g., breast, lung, and colon cancer) can escape immune detection by decreasing their expression of: class-I MHC class-II MHC CD4 CD8
Explanation: Class-I MHC is important for the recognition of virally-infected or mutated cells by cytotoxic lymphocytes. Some tumor cells escape immune detection by decreasing its expression. The other molecules listed are only found on immune (lymphoid) T-cells.
2) Occasionally, patients need to have their thymus removed (usually because of open heart surgery). Given what you know about the role of the thymus in T-cell development, which TWO of the following do you think are more common in such patients? Autoimmune diseases Infections Profound lymphocytopenia (reduced lymphocyte count) Significant Lymphocytosis (increased lymphocyte count)
Explanation: The thymus is responsible for teaching T-cells the difference between "self" and "non-self." Without proper training, T-cells are more likely to recognize self antigens (resulting in autoimmune disease), AND less likely to recognize foreign antigens (increasing the risk of infection). Since lymphocytes are born in the bone marrow, T-cell counts are not significantly affected.
3) Which of the following associations is correct: CD8+ : Cytotoxic T-cell : sees class-II MHC : on antigen presenting cells CD4+ : Cytotoxic T-cell : sees class-I MHC : on any nucleated cell CD8+ : Helper T-cell : sees class-I MHC : on any nucleated cell CD4+ : Helper T-cell : sees class-II MHC : on antigen presenting cells
Explanation: Helper T-cells are CD4+ and see peptide in the context of class-II MHC molecules on antigen presenting cells. Cytotoxic T-cells are CD8+ and see peptide in the context of class-I MHC molecules on any nucleated cell.
4) You see a patient with allergic asthma. Rather than treating the patient with systemic immunosuppression, you might try a drug that blocks: Immune complex formation IgE binding to mast cell Fc-receptors IgA dimerization Cytotoxic T-cells
Explanation: IgE bound to mast cells is the primary driver of allergic responses. Molecules that block the binding of IgE to mast cells are used to treat some cases of allergy.
5) As a tropical disease researcher you know that M. tuberculosis (TB) evades immune detection by resisting phagocyte digestion. To stimulate immunity, you come up with a new therapy where you extract these cells from a patient, dose them with TB peptides, and re-inject them into the patient's body. Macrophages T-Lymphocytes B-Lymphocytes Dendritic Cells
Explanation: Dendritic Cells are the best antigen presenting cells (better than macrophages). Since T-cells need to see peptide bound to MHC, it would do no good to dose them with peptide alone. This question is challenging!
6) As an astrobotanist you have discovered a new extraterrestrial pathogen that contains lipids and carbohydrates but no proteins. You are alarmed because you realize that this pathogen will never be recognized by: T-cells B-cells Antibodies All of the above
Explanation: T-cells recognize peptides (i.e. protein), whereas B-cells and antibodies can recognize pretty much anything (except maybe silicon-based life forms).
7) Which of the following do NOT have class I MHC molecules? Red Blood Cells Macrophages Epithelial Cells Skeletal Muscle Cells
Explanation: class I MHC molecules are found on all nucleated cells in the body. RBCs are not nucleated. Macrophages have both class I and class II MHC molecules.
Explanation: Plasma cells differentiated B-cells that are essentially antibody producing factories.
9) Which of the following is true about mast cells? They are the tissue equivalent of basophils They produce histamine They are specialized to handle parasite infections All of the above
Explanation: Mast cells secrete histamine (among other compounds) when the IgE of their surface is cross-linked by a parasite or an allergen.
10) You are encouraging a new mother to breast feed, in part because of the protective antibodies secreted in breast milk. You know that these antibodies are of which isotype: IgA IgD IgE IgG IgM
Explanation: Secreted antibody is mostly IgA, because it is capable of surviving harsh environments (like the stomach of a receiving infant).
11) Which of the following is the first antibody isotype produced during an immune response? IgM IgG IgA IgE
Explanation: IgM is the first antibody produced, the others require subsequent class switching.
12) Which isotype has the highest titer (amount) in blood serum? IgM IgG IgA IgE
Explanation: IgG makes up roughly 75% of the immunoglobulin in serum.