Test 1 Flashcards
Why was Jenner’s vaccine superior to previous methods for conferring resistance to
smallpox?
The previous method that had been used to confer smallpox immunity used material from lesions of smallpox victims. While it conferred immunity, it was still possible to contract and even die from the disease. By using cowpox to confer immunity to smallpox significantly reduced the risk of acquiring the potentially lethal disease.
Describe how Pasteur developed & tested his anthrax vaccine and why it was important.
Louis Pasteur discovered how to attenuate a pathogen and administer that attenuated pathogen to act as a vaccine. He developed the attenuated vaccine against anthrax and then set up a controlled experiment in sheep. This marks the beginning of the discipline of immunology given that we now have so many ways to develop effective vaccines.
What is herd immunity and why is it important clinically?
Herd immunity occurs when enough members of a population have protective immunity to a pathogen, either through vaccination or prior infection. These individuals act as a buffer to spread of disease and help protect those that have weak immune systems or no immunity (i.e. allergic to components of the vaccine, immunocompromised).
If vaccines are so successful, why have they been controversial for some people?
Because of a claim perpetuated in the Lancet that vaccines cause autism, this myth became
“fact” for many people, despite the article’s retraction. The timing of the peak number of
vaccinations at 2 years and the development of developmental disorders do coincide, but there
is no scientific literature that suggests that vaccines cause autism. Past controversies with
thimerosal use in vaccines also contribute to confusion for parents.
Give four examples of mild and severe consequences of immune dysfunction?
Mild – sneezing, hives, skin rash
Severe – anaphylactic shock, susceptibility to infection (immunosuppression), chronic debilitation (autoimmunity)
List three differences between innate and adaptive immunity?
1) Innate response time is fast, whereas the adaptive response is slower.
2) **Innate response specify is limited and fast, Adaptive is diverse and improve over time.
3) Innate response is the same whereas adaptive response is more rapid & effective over time
How is the recognition of antigen different between pattern recognition receptors and B and
T cell receptors?
PRR are germline-encoded receptors and recognize general pathogen associated molecular
patterns (PAMPS). This type of recognition is the hallmark of innate immunity.
B and T cell receptors are a result of DNA rearrangement and are much more diverse and respond to specific pathogens. This type of response is the hallmark of adaptive immunity.
How is clonal selection important for the adaptive immune response?
Adaptive immune receptors are randomly made using DNA rearrangement and then pathogen
specific cells are selected for based on their antigen binding from a diverse group of receptors.
This theoretically provides the ability to recognize and respond to any antigen.
The idea is that each cell has one unique receptor; this cell then proliferates in response to antigen, providing a tremendous force of immune cells specific to that antigen.
What are memory cells and why are they important for protection from infection?
Upon exposure to antigen, B and T cells clonally expand and memory cells are formed. When
exposed to the same pathogen, these memory cells respond faster and more robustly to remove
the infectious agent more efficiently.
What is the hygiene hypothesis and how does it relate to hypersensitivity reactions?
The hygiene hypothesis predicts that a lack of early childhood exposure to infectious agents and parasites increases susceptibility to allergic diseases by modulating immune system
development.
Increases in hypersensitivity reactions can be explained by alterations in the development of immune cells that were not exposed to many pathogens in development.
What is the difference between a pluripotent stem cell and a hematopoietic stem cell?
Both pluripotent and hematopoietic stem cells are able to “self-renew” and able to differentiate into different cell types.
A pluripotent stem cell possesses the capability to develop into any kind of specialized cell, regardless of cell tissue or type.
A hematopoietic stem cell, however, can only generate cells that arise from the blood and mature into specialized blood cells such as macrophages, lymphocytes, red blood cells, dendritic cells, and granulocytes.
List the cells that differentiate from the myeloid progenitors
Eosinophils
Neutrophils
Basophils
Erythrocytes
Megakaryocytes (platelets)
Monocytes
Macrophages
Dendritic cells
Mast cell
List the cells that differentiate from the lymphoid progenitors
T lymphocyte
B lymphocyte
Natural killer cell
Dendritic cell
What are the characteristics of granulocytes?
Granulocytes consist of neutrophils, basophils, eosinophils, and mast cells.
These cells are part of the innate immune system and are the immune system’s first defense against foreign invaders. Granulocytes have multi-lobed nuclei—lymphocytes’ nuclei are round.
They have granules in their cytoplasm (hence the term granulocyte) that are released when
an infection is detected. Of the granulocytes, neutrophils have the largest number of cells,
comprising 50-70% of leukocytes.
What is the difference between a monocyte and a macrophage and a dendritic cell?
These cells are derived from myeloid progenitors and all are phagocytic cells that present antigens to other immune cells such as T lymphocytes.
Monocytes are the predecessors of macrophages and dendritic cells. Monocytes can either be inflammatory or patrolling, meaning they can enter tissue or crawl along blood vessels respectively.
The monocytes that migrate into the tissue become macrophages and typically become tissue-specific, such as osteoclasts and microglial cells. Macrophages use pseudopodia to phagocytize and present antigen, becoming activated and more effective when interacting with specific antibodies or T helper cells.
Dendritic cells appear to arise from both myeloid and lymphoid progenitors. In processing antigen, dendritic cells can phagocytize or internalize it via receptor-mediated endocytosis or pinocytosis using elongated processes, then presents it to naïve T cells, activating them.
What are the three main types of lymphocytes and what is the purpose of the term “CD” in immunology?
The three main types of lymphocytes are B cells, T cells, and ** natural killer cells**.
Under a microscope, these cells look very similar; because of this, the surface markers on each of
these cells must be used to identify each type. These surface proteins are the “CD” or cluster of differentiation. By using the CD nomenclature, each of these surface proteins has a specific name associated with the CD nomenclature, such as CD4, which helps distinguish different cell subtypes.
List two primary and secondary lymphoid organs and summarize their functions in the
immune response.
The two primary lymphoid organs include the bone marrow and the thymus. Both of these
organs are where myeloid and lymphoid cells differentiate or mature; the bone marrow is
where the hematopoietic stem cells reside and B cells mature, while T cells undergo
selection and maturation in the thymus.
The bone marrow functions to develop and replenish blood cells by providing the environment necessary for those cells to grow and differentiate.
The thymus provides specific microenvironments which allow for immature T cells (thymocytes) to develop and mature into a specific type of T cell. In the thymus, the T cells generate unique receptors that are then selected based on whether or not they react to self-peptide.
Two secondary lymphoid organs include lymph nodes and the spleen.
Summarize how positive and negative selection of T cells in the thymus works.
Immature T cells enter the thymus so they can develop their T cell receptors (TCRs). When
they enter the thymus, the TCRs interact with thymic stromal cells that have self MHC peptides presented on their surface.
The T cells whose TCRs bind really tightly to those self MHC peptides will undergo negative selection and will be forced to die.
If the TCRs don’t bind too tightly or only have an intermediate affinity to the self MHC peptides (in other words, binding has to be just right), the T cell will undergo positive selection and be allowed to live and develop into a mature T cell.
Describe the three functional regions in a lymph node.
The lymph node has three distinct regions that include the cortex, the paracortex, and the
medulla.
The cortex is the outermost layer and consists of follicles full of B cells, macrophages, and dendritic cells. The cortex is connected to the body via afferent lymphatic vessels, which bring in antigen traveling as a particulate from an infected tissue
or with an antigen-presenting cell.
The paracortex is deep to the cortex and is where T cells and dendritic cells typically reside. The naïve T cells travel along fibroblast reticular cells in the paracortex to guide their movements as they sample the MHC peptides presented by the dendritic cells.
The medulla is the innermost layer and is where lymphocytes exit the lymph node via efferent lymphatic vessels, so not very many cells are found here in comparison to the cortex and paracortex.
Describe the three functional regions in a spleen.
While the lymph nodes specialize in providing interactions between antigen and lymphocytes, the spleen’s responsibility is to filter blood and trap antigens in the blood.
The three regions of the spleen include the red pulp, white pulp, and marginal zone. There is an outermost layer called the capsule which consists of trabeculae that extend out to
provide support for the spleen.
The red pulp consists of sinusoids where red blood cells, macrophages, and lymphocytes reside and is the place for old or defective red blood cells to
be destroyed.
The marginal zone separates the red and white pulp and is where macrophages and B cells make the first defense against blood-borne pathogens.
The white pulp consists of T cells and B cell follicles, where germinal centers generate more B cells with increased receptor affinity.
What is a M cell and why is it important in mucosa associated lymphoid tissue?
An M cell is a specialized epithelial cell residing in the digestive tract’s mucosa-associated
lymphoid tissue that transports antigen across the epithelium.
They accomplish this by using a deep pocket that contains B cells, T cells, macrophages and dendritic cells. Antigens are trapped in vesicles, then transported to this pocket membrane; the cells residing in the pocket process the antigen then travel below the epithelium to activate B cells. These B
cells differentiate into plasma cells and produce IgA antibodies that target the mucosal infection. This provides an effective tool in protecting the digestive system.
What is different about jawless and fish with jaws regarding their immune systems?
Fish with jaws have more structured primary and secondary lymph structures, such as the thymus and spleen.
Jawless fish, on the other hand, do not have such structural organization in their immune system.
It was thought that the jawless fish didn’t have
thymic tissue, but they have found that there are distinct populations of cells similar to T
and B cells and they might have thymic tissue near their gills.
Describe what the terms cytokine, interleukin, and chemokine mean.
Cytokines refer to molecules that communicate among immune cells. They are generally
soluble molecules which bind to receptors on target cells and cause changes in the expression
of adhesion molecules and chemokine receptors, affect enzymatic or transcriptional factor
activity, or instruct a cell when to live or when to die.
Interleukins are derived from the Latin
words inter (between) and leukocytes (white blood cells) and is a term typically used in naming different cytokines.
A chemokine refers to a specific kind of cytokine that serve to mobilize immune cells from one organ or tissue to another. These molecules attract cells with the right chemokine receptors to where chemokine concentration is the highest.
Cytokines can be further classified by the distance they are secreted: endocrine (pass through the
bloodstream), paracrine (very short distances between cells or tissues), or autocrine (cell
signals itself).
Describe pleiotropy, redundancy, synergy, and antagonism.
Pleiotropy means that one cytokine has multiple target effector cells that it affects.
Redundancy implies that different cytokines cause or do the same function (not summation).
Synergy means that two or more cytokines work together to produce a specific effect (summation).
Antagonism is where one cytokine blocks or antagonizes the actions of another.