Intro to Immuno

Question 1

What is plasma?

Answer 1

What remains from a blood sample after the erythrocytes (RBCs) and leukocytes (WBCs) have been removed. Plasma contains clotting factors, antibodies, complement proteins, etc..

Question 2

What is serum?

Answer 2

a clear yellowish fluid that remains from a blood sample after it has been allowed to clot and all of the cells (RBCs and WBCs) have been removed. Serum contains antibodies and complement proteins.

Question 3

What is a titer?

Answer 3

a term that refers to the concentration of antibodies that have specificity for a particular antigen

Question 4

What is inflammation?

Answer 4

part of the body’s response to injury, and it consists of redness, heat swelling, and pain.The suffix –itis means inflammation

Question 5

What does the suffix –penia mean?

Answer 5

indicates a deficiency of something: e.g. neutropenia means that a patient has abnormally low numbers of neutrophils; leukopenia means that the patient has abnormally low numbers of white blood cells; etc.

Question 6

What do the suffixes –cytosis and –philia mean?

Answer 6

indicate an elevated number of white cells in the peripheral blood. Elevated numbers of cells can be indicative of clinical conditions such as infection.

Question 7

What are bands or band forms?

Answer 7

immature neutrophils that can be seen on a blood smear. During a serious bacterial infection, the body’s stores of neutrophils can be depleted, resulting in production of large numbers of new neutrophils in the bone marrow. The newly generated neutrophils in this case are released into the blood before they have matured and they have a characteristic appearance because their nuclei have not segmented yet.

Question 8

What is the difference between the roles of the innate and acquired immune system?

Answer 8

The role of the innate immune system in a general sense, is to prevent or control infection while the acquired immune response is being generated so that the infected host (or patient) does not suffer too much infection-mediated damage. Once the acquired immune response is generated, it can clear the infection with high specificity and efficiency. Over the next few weeks, we will talk about each of the innate immune “responses” and the acquired immune responses, as well as the mechanisms that result in removal of the infectious agent from the host’s tissues.

Question 9

What are some of the key characteristics of the innate immune system?

Answer 9

In all people, the innate immune response is essentially the same. It provides protection from pathogenic insult starting with initial encounter, and it continues to control an infection for about the first 4-5 days post exposure (rapid response). The specificities of the innate immune system are fixed and very limited. This means that the specificities of innate responses are essentially identical in all immunocompetent hosts, and they don’t change in response to any specific infection. These specificities recognize only general features of a pathogen, such as LPS (which is found on all gram-negative bacteria). The innate immune response remains constant over the course of an infection. The innate immune responses will always be the same each time a specific pathogen is encountered.

Question 10

What are some of the key characteristics of the acquired immune system?

Answer 10

Adaptive responses are not preformed, and generating these responses takes some time (at least a week after initial exposure to the pathogen).The acquired response is highly variable. The effector cells of adaptive responses (lymphocytes) have a huge array of possible specificities that are highly specific for potentially any product made by any pathogen. The adaptive immune response also improves over the course of the immune response. The adaptive immune response involves clonal expansion and memory of the response that makes it much more effective upon any additional encounter with that specific pathogen in the future.Finally, it is important to note that some of the effector mechanisms that are employed by the acquired immune system are dependent on components of the innate immune system.

Question 11

T or F. The innate immune system has a limited array of specificities that are limited mostly to common determinants of pathogens.

Answer 11

T. These specificities are determined by what are known as pattern recognition receptors (or PRRs). These receptors recognize what we will call PAMPS, or pathogen-associated molecular patterns.In contrast, the cells of the acquired immune system (B cells and T cells) express highly specific receptors that recognize discreet structures of a particular pathogen. The receptors on a single B or T cell are all the same and all cells are unique

Question 12

Overview of the complement cascade.

Answer 12

there are a series of proteins found in the serum and in the extravascular spaces of the body that are expressed at constitutive levels at all times (whether an infection has occurred or not). Each of these pathways can be initiated innately, and once they are initiated, there are three end products that help to control or eliminate infectious agents (primarily bacterial or even fungal agents):(1) inflammatory mediators called anaphylatoxins,(2) opsonins (or permanently attached tags that mark the pathogen for uptake and destruction by neutrophils and macrophages), and(3) the membrane attack complex or MAC (a structure that inserts into bacterial outer envelopes, resulting in death of the bacterium).

Question 13

What are primary lymph tissues responsible for? What are they?

Answer 13

these are where all immune cells are generated. These are the bone marrow (where all precursor immune cells are generated) and the thymus (where thymocytes migrate to and undergo their development into mature naïve T cells).The secondary lymphoid tissues are where all acquired immune responses are initiated.

Question 14

How are immune cells derived in bone marrow? (The immune cascade)

Answer 14

There is a single progenitor cell, called the hematopoietic stem cell that gives rise to three progenitor cells:1. The common erythroid/megakaryocyte progenitor gives rise to erythrocytes (red blood cells) and megakaryocytes. Megakaryocytes give rise to platelets, which (as you probably know) are critical for clotting. 2. The common myeloid progenitor gives rise to most of the purely innate immune cells. These include the granulocytes (neutrophils, eosinophils, and basophils), dendritic cells, monocyte/macrophages, and mast cells.3. The common lymphoid progenitor gives rise to one purely innate cell type (NK cells) as well as the two cells that comprise the adaptive immune system (B cells and T cells) that are collectively known as lymphocytes.

Question 15

What is the role of erthrycytes?

Answer 15

RBCs have an important role in the clearance of immune complexes from the circulation,

Question 16

What is the role of megakaryocytes?

Answer 16

megakaryocytes produce platelets, or thrombocytes.

Question 17

What are Neutrophils?

Answer 17

purely innate cells that recognize pathogens via their pattern recognition receptors, signaling them to engulf and kill the microbe.The primary role of these cells is to control bacterial and fungal infectionsThese cells are considered granulocytes. This term reflects that they have a large number of cytoplasmic granules (that are critical to their function) that are easily visible upon staining. They are also often referred to as polymorphonuclear cells, or PMNs, because of their multi-lobed nucleus.NOT anitgen presenting cells

Question 18

What is a band cell?

Answer 18

Bands are immature neutrophils that can be distinguished from mature neutrophils by their nucleus that is not yet segmented.

Question 19

When are band cells common?

Answer 19

During bacterial infections, neutrophils are essentially the marines of the immune system. Large numbers of them move into the infected tissue and take up bacteria and kill them. However, they are essentially kamikazes and have a short lifespan. If the bacterial infection is serious enough, the body’s stores of mature neutrophils will be exhausted and new neutrophils will be generated in the bone marrow and then released into the bloodstream as immature cells (bands). The presence of bands can help a physician to diagnose a condition as a bacterial infection.

Question 20

What is the precursor to a macrophage?

Answer 20

a monocyte. They do not really have any function until they leave the vasculature, move into tissues and become mature macrophages.

Question 21

What are macrophages?

Answer 21

the mature version of a monocyte that has entered and patrols extravascular tissues. They are multifunctional cells that have important roles in the innate immune response: namely, to recognize, engulf, and destroy potential pathogens that it recognizes via its many pattern recognition receptors.Macrophages also have complement receptors that allow them to recognize foreign material that has been labeled with complement opsonins. When this occurs, they take up and destroy the material.

Question 22

Do macrophages also participate in acquired immune response?

Answer 22

Yes, They are one of the three professional antigen presenting cell types (plus dendritic and B cells) that can activate naïve T cells, and they express antibody Fc receptors that allow them to be bridged into an acquired immune response.

Question 23

What are eosinophils?

Answer 23

Eosinophils are another of the granulocytes. The primary role of these cells is to control PARASITE infections. Their granules contain inflammatory mediators and compounds that are toxic to parasites. Purely Innate immune response cellThey also have IgE receptors on their surface.

Question 24

What are basophils?

Answer 24

The last of the granulocytes are the basophils. Purely innate immune cell response. These are the least abundant granulocyte, and their function remains somewhat un-defined. Have IgE receptors on their surface.They probably have similar effector mechanisms to eosinophils.

Question 25

What are mast cells?

Answer 25

Purely innate immune response cells. Are involved in protection against parasite pathogens. Their granules contain very potent inflammatory mediators, and they also have high affinity IgE antibody receptors on their surface.The main focus our our discussions of these cells will relate to their role in immediate-type hypersensitivity responses like hay fever, asthma, and systemic anaphylaxis.This is a very important cell type for you to know about because of the extreme clinical condition that results when they are activated in a systemic fashion.

Question 26

What is mastocytosis?

Answer 26

A rare condition in which patients have an overabundance of mast cells.

Question 27

What are the primary forms of mastocytosis?

Answer 27

(1) cutaneous- where the excessive numbers of mast cells are primarily found in the skin, and (2) systemic- where excessive numbers of mast cells populate internal organs and/or the skinThe disease is often early onset, and it usually presents early in life as the cutaneous form. Later in life the condition is more likely to have systemic presentation.

Question 28

Mastocytosis results from from a genetic mutation in the ____ gene.

Answer 28

c-kit

Question 29

What is the most common mutation of the c-kit gene in masotcytosis?

Answer 29

substitution of an aspartic acid residue to a valine at codon 816 of exon 17 of the c-kit gene. The mutation is likely to be noted as D816V.

Question 30

What are natural killer cells (NK cells)?

Answer 30

Natural killer cells (or NK cells) are another purely innate cell type, despite the fact that they are derived from the common lymphoid progenitor. These cells are very similar to one of the T cell types we will discuss later except that they do not express antigen-specific receptors.NK cells have an important role in the innate control of virus infections.They can also be enlisted into an acquired immune response (because they express Fc receptors), and in this regard they are the effectors of antibody-dependent cell-mediated cytotoxicity (or ADCC). This is a mechanism of recognition and killing of host cells that are infected with a pathogen, preventing the pathogen’s replicative cycle from being completed.

Question 31

How do macrophages cause inflammation?

Answer 31

A tissue macrophage encounters a bacterial pathogen and recognizes it through its pattern recognition receptors (PRRs). PRR engagement results in production of inflammatory mediators (known as cytokines) and chemotactic factors (chemokines) that cause inflammation and cell recruitment.

Question 32

Why is inflammation critical to causing a secondary immune response?

Answer 32

The resulting inflammation is important to the innate control of infections, and it is critical for the initiation of adaptive (or acquired) immune responses because it promotes movement of antigens and antigen-presenting cells into the nearest secondary lymphoid tissues.All acquired immune responses are initiated within secondary lymphoid tissues.

Question 33

What is the role of the spleen?

Answer 33

A secondary lymph organ that serves essentially as a blood filter. It also is a site for storage of new RBCs as well as for removal of old RBCs.

Question 34

What is the site in the spleen for storage of new RBCs and removal of old RBCs?

Answer 34

red pulp

Question 35

Describe white pulp in the spleen.

Answer 35

Each of the areas of white pulp has a highly organized arrangement that includes a T cell zone (known as the periarteriolar lymphoid sheath) that is adjacent to a central arteriole. There is also a B cell zone that is divided into three regions (the marginal zone, the B cell corona, and the germinal center). Know that germinal centers are within the B cell zone

Question 36

What is in high concentration in the T zone of the spleen?

Answer 36

occupied by dendritic cells and macrophages (professional antigen presenting cells), and it is immediately adjacent to the B cell zone.

Question 37

What is the significance of the T zone being right next to the B zone?

Answer 37

This arrangement allows for high contact between T cells and antigen presenting cells, as well as high contact between B cells and effector T cells that occupy the T cell zone.

Question 38

How are lymph nodes organized?

Answer 38

Secondary lymph organ. Lymph fluid that carries antigens and antigen presenting cells from inflamed tissues are transported into the lymph node via the afferent lymphatic vessels. The T cell zones are populated with these antigen presenting cells. The efferent lympatic vessels carry lymph out of the lymph node, emptying either into another lymph node (as its afferent lymph vessel) or into one of the lymph ducts. Both the lymph ducts return the lymph to the blood stream by emptying into veins.

Question 39

How are Peyer’s patches organized?

Answer 39

The basic organization of a Peyer’s patch is very similar to that of the spleen white pulp or lymph nodes: it has a concentrated T cell zone that is occupied by antigen presenting cells and an adjacent B cell zonePeyer’s patches have efferent lymphatics that transport antigen and APCs to lymph nodes

Question 40

What are microfold cells?

Answer 40

Cells found in Peyer’s patches that sample antigens from the lumen of the gut, transporting those antigens into the Peyer’s patch for antigen presentation to T cells and sampling by B cell receptors.

Question 41

T or F. greater than 50% of the immune cells in the body are distributed into mucosal tissues that line the mucosal surfaces of the body

Answer 41

T. Other than the Peyer’s patches, these tissues are not as well organized as those we have discussed, but the same basic principles apply.Collectively, the mucosal-associated lymphoid tissues are referred to as the MALT. The gut-associated lymphoid tissues are referred to as the GALT. The conjunctiva-associated lymphoid tissues are called the CALT The nasal-associated lymphoid tissues are referred to as the NALT.

Question 42

What three different immune cell types are involved in antigen presentation to naïve T cells?

Answer 42

Two of these are purely innate cells (dendritic cells and macrophages), while the other is a cell of the adaptive immune system (B cells).Presentation of antigen to naïve T cells is the first step in generating an acquired immune response.

Question 43

What are the most potent of the antigen presenting cells?

Answer 43

dendritic cells. these innate cells have a unique morphology that gives them a tremendous amount of surface area. This is critical to their function because it allows them to interact with many naïve T cells at the same time.

Question 44

What are the roles of macrophages?

Answer 44

Is a component of both innate and acquired immune responseIs a professional antigen presenting cell, has many pattern recognition receptors that allow it to recognize and destroy bacterial and fungal pathogens, and has complement and Fc receptors that allow it to find and destroy opsonized microbes

Question 45

T or F. The innate immune system typically does not clear infections once they are well-established, but they can control the infection and allow the host (or patient) to survive until a highly efficient adaptive immune response can be generated.

Answer 45

T. Once an acquired immune response is generated, the infection can be efficiently cleared in most cases. The acquired immune response is made up of two “arms”: humoral, or antibody mediated, and T cell-mediated immunity

Question 46

What types of cells are involved in secondary lymph response?

Answer 46

lymphocytes

Question 47

What are the two types of lymphocytes involved in secondary immune response?

Answer 47

B and T cells

Question 48

What do B cells do?

Answer 48

produce and secrete antibodies

Question 49

What do T cells do?

Answer 49

these cells can be further subdivided into CD4+ and CD8+ T cells. Effector CD4 T cells modulate the activity of other immune cell types through their production of protein signals known as cytokines, while CD8 effector cells recognize and kill infected host cells.Each immunocompetent individual has many millions of B cells and T cells that all have distinct antigen specificities.

Question 50

T or F. Some pathogens live inside of host cells while others live in extracellular spaces within the body. The immune system must make this determination because different types of immune responses are required for clearing these two types of infections

Answer 50

T.

Question 51

What is the best response for controlling extracellular pathogens using the acquire immune system?

Answer 51

Antibody-mediated responses

Question 52

What is the best response for controlling intracellular pathogens using the acquire immune system?

Answer 52

T cell-mediated responses

Question 53

What is somatic recombination?

Answer 53

mechanism that allows for the generation of a tremendously diverse repertoire of lymphocyte receptors for specific antigen recognition, and how one of those lymphocytes can be identified, activated, clonally expanded, and then how they perform their effector function.Somatic recombination utilizes a cassette system that allows for a relatively small amount of DNA to encode an enormous repertoire of antigen-specific receptors.

Question 54

What are the two basic structures of antigen receptors of B and T lymphocytes?

Answer 54

Antibodies (the antigen-specific receptors and effector molecules of B cells).T cell receptors (the antigen-specific receptors of T cells)

Question 55

What is an antigen (antigenic determinants)?

Answer 55

any ligand that binds to B or T cell receptors (BCR or TCR).

Question 56

What is a major difference between he binding capabilities of antibodies (from B cells) and T cell receptors?

Answer 56

antibodies can bind to almost any form of antigen (particulate or soluble), composition of antigen (protein, carbohydrate, nucleic acid, lipid, etc). ***In contrast, T cells only recognize peptide antigens (short pieces of protein) that are displayed on one of two types of host proteins (these are known as MHC- major histocompatibility complex- molecules).

Question 57

What are MHCs (major histocompatibility complex)?

Answer 57

In a nut shell, these are the proteins that bind to and display peptide antigens for T cell recognition.

Question 58

Where are MHC class I molecules found in the body?

Answer 58

found on all nucleated cells in the body

Question 59

Where are MHC class II molecules found in the body?

Answer 59

found only on antigen presenting cells.This distribution of MHC expression reflects the effector mechanisms mediated by the T cells that sample antigen on these two proteins

Question 60

One of the T cell lineages, the ___ T lymphocytes, are responsible for recognizing and killing infected host cells.

Answer 60

CD8+

Question 61

What is the MHC class I processing and presentation pathway?

Answer 61

1. Virus infects cell2. Viral proteins synthesized in cytoplasm3. Bound peptides transported by MHC class I to the cell surface4. Cytotoxic T cell recognizes complex of viral peptide with MHC class I and kills infected cell*CD8 T cells only recognize antigens presented through this pathway (they are MHC class I-restricted)

Question 62

What is the the MHC class II processing and presentation pathway?

Answer 62

1. cell surface immunoglobulin of B cell binds bacteria, the cell engulfs and degrades them, producing peptides2. Bacterial peptides bound by MHC class I in endocytic vesicles3. Bound peptides by MHC class II to the cell surface4. Helper T cell recognizes complex of peptide antigen with MHC class II and activates B cell via a very specific signalCD4 T cells only recognize antigens presented through this pathway (they are MHC class II- restricted)

Question 63

How are B cells activated by helper T cells?

Answer 63

T cells have activation requirements to activate the B cells, but also have activation requirements to prevent activation of host-specific immune responses that would result in autoimmune responses

Question 64

What are plasma cells?

Answer 64

a terminally differentiated effector B cell.You will note that plasma cells have a very large cytoplasm that is filled with an extensive endoplasmic reticulum. This reflects the role of this cell type as an antibody factory (because the ER is the secretory network of the cell).

Question 65

Are antibodies themselves destructive to pathogens?

Answer 65

NO. antibodies themselves are not destructive to pathogens. Antibodies primarily serve as bridges between the innate immune system and the acquired immune response by activating innate immune cells to perform their effector function.