Exam 1: Basic Concepts in Immunology

A common mechanism by which sensor cells in the host detect micro-organisms relies on the production of unique microbial components not found in the host. Propose a strategy by which a clever microbe could evade this type of response.

Innate lymphoid cells and NK cells are effector cells that respond rapidly after encountering a pathogen. Several different subsets of innate lymphoid cells exist, and each is specialized to respond to a category of pathogen (e.g., viruses, extracellular bacteria, helminthic parasites, etc). Innate lymphoid cells reside primarily in tissues such as the lungs, the lining of the gastrointestinal tract, and the skin, because these sites represent the major routes of entry of pathogens into the body.

One factor that contributes to the enhanced secondary response to an antigen is the increased number of antigen-specific lymphocytes present after the primary response; these are known as memory cells.

The majority of vaccines work by eliciting pathogen-specific antibodies that circulate in our bodies and protect us in the event that we are later exposed to that specific pathogen. For most viruses and bacterial toxins that we are vaccinated against, these pre-existing antibodies are protective because:

Adaptive immune responses are slow to develop, taking days to weeks after exposure to reach their peak. However, these responses are more specific than innate responses, and also generate immunological memory. These latter features, which provide enhanced protection upon re-infection with the same pathogen, are the basis of:

Some Pattern Recognition Receptors (PRRs) recognize nucleic acids, like RNA or DNA. Since our own cells contain human RNA and DNA, the activation of innate immune pathways by these PRRs must rely on additional criteria to discriminate self from nonself. Additional criteria include everything EXCEPT:

The immune system evolved to protect us against infections from pathogenic microorganisms. However, immune responses can also cause, rather than prevent disease. Give two examples of situations in which an immune response causes a disease, whereas the absence of a response has no consequences.

When macrophages in a tissue encounter bacteria, they release cytokines that induce an inflammatory response. These cytokines act on other immune cells, to recruit them to the site of infection and to enhance their activities. In addition, these cytokines act on the endothelial cells of the blood vessel wall to:

Inherited immunodeficiency diseases result from a single gene defect in one component of the immune system. By identifying the class of microbial pathogens a given immunodeficient individual becomes susceptible to, studies of these diseases indicate:

Dendritic cells are phagocytic, but also capable of ingesting large amounts of extracellular fluid and its contents, a process known as macropinocytosis. What specialized function do dendritic cells have in immunity that might account for their need to perform macropinocytosis?

Dendritic cells, also called 'antigen-presenting-cells' are considered the bridge between the innate and the adaptive immune responses. Describe two key features of dendritic cells that are essential for them to provide this bridging function.

The antibody protein is often depicted as an uppercase letter Y, with the two variable regions (antigen-binding domains) pointing up, and the stem consisting of the Fc region (constant domain). An analogy has been made between an antibody protein and a guided missile, with one type of antibody domain functioning as the guidance system, and the other type of domain as the 'payload.' Which antibody domain serves as the guidance system, and which as the payload? Explain your answer.

Given the enormous heterogeneity of antigen receptors expressed on the populations of naive B and T lymphocytes, the adaptive immune response relies on a process whereby the rare lymphocyte that binds to the antigen is first induced to proliferate, before it can perform its effector function. For B cells, there is a clever mechanism that ensures that the specificity of the antibody secreted by the plasma cell will recognize the same pathogen that initially stimulated the B cell antigen receptor and induced B cell proliferation. This mechanism is:

Lymph nodes function as meeting points between antigen-bearing dendritic cells arriving from the tissue and recirculating B and T lymphocytes. Whereas the dendritic cells coming from the tissue enter the lymph node via the afferent lymphatic vessels, the recirculating lymphocytes enter the lymph node:

Unlike B lymphocytes, T lymphocytes do not generate a secreted form of their antigen receptor after they are activated and proliferate. This is because the effector functions of T cells are restricted to:

Vaccination against many infectious diseases has provided enormous benefit in developed countries, leading to the virtual eradication of diseases such as polio, measles, smallpox, and others. However, efforts to create long-lasting vaccines against some viral infections, like Influenza and HIV, have not been successful to date because:

Secondary (or peripheral) lymphoid organs are sites for initiation of adaptive immune responses. Given the rarity of lymphocytes specific for any given antigen and the vast amount of body tissue that must be protected, the system of secondary lymphoid tissues is efficient because:

Most B and T lymphocytes in the circulation appear as small, inactive cells, with little cytoplasm, few cytoplasmic organelles, and nuclei containing condensed inactive chromatin. Yet these cells comprise the adaptive immune response, without which individuals die in infancy. What is the explanation for this apparent dichotomy?

In patients with lymphomas, the cancer cells invade the bone marrow and destroy the environment required for normal hematopoiesis. This leads to bone marrow failure, which disrupts the production of hematopoietic cell lineages. All of the following cell types would be affected by this EXCEPT:

The best evidence supporting the concept of immunological memory is: