Immune System

Mast cells

-a cell filled with basophil granules, found in numerous quantity in connective tissue that releases histamine and other substances during inflammatory and allergic reactions -it is a type of granulocyte derived from the myeloid stem cell that is a part of the immune and neuroimmune systems -it contains many granules rich in histamine and heparin -they are IgE-primed cells that release granules and powerful chemical mediators, such as histamine, cytokines, granulocyte macrophage colony-stimulating factor (GM-CSF), leukotrienes, heparin, and many proteases into the environment. -these chemical mediators cause the characteristic symptoms of allergies

Antigen presenting cells

-a cell that displays antigen complexed with major histocompatibility complexes (MHCs) on their surfaces -T cells may recognize these complexes using their T cell receptors (TCRs) -they are a heterogeneous group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by certain lymphocytes such as T cells -classical forms of these cells include dendritic cells, macrophages, Langerhans cells and B cells

Toll-like receptors

-a class of proteins that play a key role in the innate immune system -they are single, membrane-spanning, non-catalytic receptors usually expressed in sentinel cells such as macrophages and dendritic cells -they recognize structurally conserved molecules derived from microbes and activate signaling pathways that launch immune and inflammatory responses to destroy the invaders

Leukocytes

-a colorless cell that circulates in the blood and body fluids and is involved in counteracting foreign substances and disease -there are several types, all amoeboid cells with a nucleus, including lymphocytes, granulocytes, monocytes, and macrophages

Lymphocytes

-a form of small leukocyte with a single round nucleus, occurring especially in the lymphatic system

Interferons

-a group of signaling proteins made and released by host cells in response to the presence of several pathogens, such as viruses, bacteria, parasites, and also tumor cells -they belong to the large class of proteins known as cytokines, used to trigger the immune system -they "interfere" with viral replication by protecting cells from virus infections -they activate natural killer cells and macrophages -a virus-infected cell releases viral particles that can infect nearby cells, but the infected cell can prepare neighboring cells against a potential infection by the virus by releasing these agents

Macrophage

-a large phagocytic cell found in stationary form in the tissues or as a mobile white blood cell, especially at sites of infection -it is a type of phagocyte, responsible for detecting, engulfing and destroying pathogens and apoptotic cells -they are produced through the differentiation of monocytes when they leave the blood -they are versatile cells that play many roles, such as scavengers that rid the body of worn-out cells and other debris -along with dendritic cells, they are foremost among the cells that present antigens, a crucial role in initiating an immune response

Memory cell

-a long-lived lymphocyte capable of responding to a particular antigen on its reintroduction, long after the exposure that prompted its production

Major histocompatibility complex

-a set of cell surface proteins essential for the acquired immune system to recognize foreign molecules and determine histocompatibility -its main function is to bind to antigens derived from pathogens and display them on the cell surface for recognition by the appropriate T-cells -they are molecules that mediate interactions of leukocytes with other leukocytes or with body cells

Cytokines

-any of a number of substances, such as interferon, interleukin, and growth factors, that are secreted by certain cells of the immune system and have an effect on other cells -they are a large group of proteins, peptides or glycoproteins that are secreted by specific cells of the immune system -they are a category of signaling molecules that mediate and regulate immunity, inflammation and hematopoiesis

External innate immune system

-barriers of the this type of immune system include the skin and mucus secretions; chemical barriers like low pH, salt and enzymes; and cellular barriers of commensal micro-organisms -phagocytes confront microorganisms that breach the the barriers of this system

Granulocytes

-cells of the innate immune system named for the dense granules, containing reactive oxygen compounds and cytokines in their cytoplasm -they include basophils, eosinophils, and neutrophils

Lysozyme

-degrades bacterial cell walls and causes them to lyse, or burst -found in saliva, tears, and mucus

Eosinophils

-granulocytes responsible for killing parasites

Basophils

-granulocytes that are responsible for releasing histamine and mediating allergic reactions

Cytotoxic T-cells

-it is a T lymphocyte that kills cancer cells, cells that are infected (particularly with viruses), or damaged cells -they become activated when they are presented with peptide antigens by MHC molecules, which are expressed on the surface of antigen-presenting cells -once activated, they divide rapidly and secrete small proteins called cytokines that regulate or assist in the active immune response

Active immunity

-it is the immunity that results from the production of antibodies by the immune system in response to the presence of an antigen -it can be acquired naturally, which occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary response -it may also be artificially acquired, which can be induced by a vaccine, a substance that contains an inactive form of the antigen

Neutrophils

-it is the most common of the granulocytes that are responsible for phagocytosing, or eating bacteria and mediating inflammatory responses

Respiratory tract

-lined w/ mucus to trap incoming pathogens -mucus can either be expelled through coughing, eliminating harmful microbes from the body, or swallowed

Pathogen Associated Molecular Patterns

-molecules associated with groups of pathogens, that are recognized by cells of the innate immune system -these molecules can be referred to as small molecular motifs conserved within a class of microbes -they are recognized by toll-like receptors (TLRs) and other pattern recognition receptors (PRRs), and activate innate immune responses, protecting the host from infection, by identifying conserved non-self molecules -bacterial lipopolysaccharides (LPS), and endotoxins found on the cell membranes of gram-negative bacteria, are considered to be the prototypical class of this term -others include bacterial flagellin, lipoteichoic acid from gram-positive bacteria, peptidoglycan, and nucleic acid variances in viruses, such as double-stranded RNA (dsRNA)

Intercellular pathogens

-most microorganisms are destroyed by the host tissues through processes which usually involve phagocytosis and lysosomal disruption -however, some organisms are capable of growing inside macrophages and avoiding destruction -they cannot reproduce outside their host cell, meaning that their reproduction is entirely reliant on intracellular resources -they can include viruses, certain bacteria, and closely related species -protective immunity includes NK cells, and cytotoxic T cells

Flora

-nonpathogenic microbes that compete for resources and thus prevent pathogen occupancy

Dendritic cells

-phagocytic cells that kill extracellular pathogens -they recognize pathogen associated molecular patterns (PAMPs) -following phagocytosis, they present microbial antigens to cells of the adaptive immune system leading to their activation

Innate immune system

-refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body -these mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body -complement activation and inflammation, phagocytes, neutrophils, basophils, eosinophils, natural killer cells (NK), macrophages, toll-like receptors (TRLs), pathogen-associated molecular patterns (PAMPs), chemical secretions, lysozymes, antimicrobials, interferons, leukocytes and dendritic cells are all a part of this system

Passive immunity

-the transfer of active humoral immunity in the form of ready-made antibodies -it can occur naturally when maternal antibodies are transferred to the fetus by the placenta -they can also be induced artificially, when high levels of antibodies specific to a pathogen or toxin are transferred to non-immune persons through blood products that contain antibodies, such as in immunoglobulin therapy or antiserum therapy -it is used when there is a high risk of infection and insufficient time for the body to develop its own immune response, or to reduce the symptoms of ongoing or immunosuppressive diseases

B cells

-these are a type of white blood cell of the lymphocyte subtype -they function in the humoral immunity component of the adaptive immune system by secreting antibodies -additionally, they present antigens and secrete cytokines -they mature in the bone marrow, which is at the core of most bones -unlike the other two classes of lymphocytes, (T cells and natural killer cells) they express cell receptors on their cell membrane -these receptors allow these cells to bind to a specific antigen, against which it will initiate an antibody response

Immunoglobulins

-these are glycoproteins that function as antibodies that highlight structure rather than function -they can be found attached to the B-cell membranes, in secretions or circulating in blood -they are produced as a response to the detection of foreign molecules in our body (antigens) -they are major components of the humoral immune response system, and are synthesized by lymphocytes and plasma cells -they are found in the serum and in other body fluids and tissues, including the urine, spinal fluid, lymph nodes, and spleen -each adheres to and reacts only with the specific antigen for which it was produced

Antigens

-these are large molecules, usually proteins, on the surface of cells, viruses, fungi, bacteria, and some non-living substances such as toxins, chemicals, and foreign particles

Antimicrobial peptide

-these are part of the innate immune response and found amongst all classes of life -potent, broad spectrum antibiotics with novel therapeutic agents -can kill Gram negative and Gram positive bacteria, enveloped viruses, fungi and even transformed or cancerous cells -unlike the majority of conventional antibiotics, it can function as immuno-modulators

Helper T cells

-these cells are a type of T cell that play a role in the adaptive immune system -they help the activity of other immune cells by releasing T cell cytokines and help suppress or regulate immune responses -they are essential in B cell antibody class switching, in the activation and growth of cytotoxic T cells, and in maximizing bactericidal activity of phagocytes such as macrophages -when these cells are mature, they express the surface protein CD4 and are referred to as CD4+ T cells -for example, when an antigen-presenting cell expresses an antigen on MHC class II, this cell will aid those cells through a combination of cell-to-cell interactions and release of cytokines

Dendritic cells

-these cells are a type of antigen-presenting cell of the immune system -their main function is to process antigen material and present it on the cell surface to the T cells -they act as messengers between the innate and the adaptive immune systems -they are present in tissues in contact with the external environment, such as the skin (Langerhans cell), and the inner lining of the nose, lungs, stomach and intestines -they can also be found in an immature state in the blood -once activated, they migrate to the lymph nodes where they interact with T cells and B cells to initiate and shape the adaptive immune response -at certain development stages they grow branched like projections, and give way to the cell's Greek name for "tree"

Natural killer lymphocytes

-these cells are a type of cytotoxic lymphocyte critical to the innate immune system -their role play is similar to that of cytotoxic T cells where they function to eliminate the antigen, either by releasing antibodies (in the case of B cells), cytotoxic granules (cytotoxic T cells) or by signaling to other cells of the immune system (helper T cells)

Macrophages

-these digest dying cells, especially in the spleen where red blood cells die -they can also present antigens, but not as effectively as dendritic cells

Extracellular pathogens

-these do not invade cells, but instead they proliferate in the extracellular environment which is enriched with body fluids -some of them don't even penetrate body tissues (e.g. V. cholerae), but adhere to epithelial surfaces and cause disease by secreting potent toxins -although bacteria such as E. coli and P. aeruginosa are termed noninvasive, they frequently spread rapidly to various tissues once they gain access to the body -they do not have the capacity to survive the intracellular environment or to induce their own uptake by most host cells -protective immunity includes complement, phagocytosis, antibodies (especially IgA), and antimicrobial peptides

Monocytes

-these include macrophages and dendritic cells

Natural killer cells

-they naturally attack and kill cells that contain intracellular pathogens or display abnormal surface antigens, such as tumor cells

Plasma cell

-this cell is a fully differentiated B cell that produces a single type of antibody and is made in bone marrow

Barriers of the immune system

-this defense includes the skin, mucous membranes, tears, earwax, mucus, and stomach acid -it also includes the normal flow of urine that washes out microorganisms that enter the urinary tract -this system uses white blood cells and antibodies to identify and eliminate organisms that get through the body's natural barriers

Complement of the innate immune system

-this is a part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism -it promotes inflammation, and attacks the pathogen's plasma membrane -it is a system of plasma proteins that can be activated directly by pathogens, or indirectly by pathogen-bound antibody -this leads to a cascade of reactions that occurs on the surface of pathogens and generates active components with various effector functions

Antibody

-this is a protein that is also known as immunoglobulins (Ig) -they are Y-shaped blood proteins that are produced mostly by plasma cells in the immune system to help stop, or neutralize intruders and pathogens from harming the body -each protein binds to a specific antigen like a lock and key fit -when an intruder enters the body, the immune system springs into action against these invading antigens, which can be viruses, bacteria, or other chemicals -they combine chemically with substances that the body recognizes as alien in the blood and help phagocytic cells, amongst other immune cells, to bind to the intruders for recognition and destruction

Adaptive immune system

-this is a subsystem of the overall immune system that is composed of highly specialized, systemic cells and processes that eliminate pathogens or prevent their growth -the defense responses of this system are more efficient and faster than the first line of defense, if the antigen is already known -it can remember the antigens from producing memory cells

Phagocytes

-this is a type of cell within the body capable of engulfing and absorbing bacteria and other small cells and particles -they protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells

Human immunodeficiency virus (HIV)

-this is a virus responsible for acquired immunodeficiency syndrome (AIDS), leading to a loss of immune function -when the cause of death is written as complications related to AIDS, this indicates that the individual succumbed to infections caused by pathogens that are typically harmless to healthy individuals

Inflammation

-this reaction occurs when tissues are injured by bacteria, trauma, toxins, heat, or any other cause -the damaged cells release chemicals including histamine, bradykinin, and prostaglandins -these chemicals cause blood vessels to leak fluid into the tissues that causes swelling -alerts mast cells nearby to release histamines -histamines increase blood flow to the sites of infection, bringing phagocytes and other immune cells that neutralize pathogens -causes the skin to swell, redden, and become swollen and painful

Self-tolerant

-this term is an immune response that does not respond to normal cellular antigens and recognizes certain ones as non-threatening cells to the body -a term that describes a healthy adaptive immune system that does not respond to normal cellular antigens

Autoimmune disease

-what is a disease in which the adaptive immune system targets healthy body cells?

Cytotoxic T cells

-when activated, its toxicity will kill a host cell that expresses a foreign antigen -these cells are antigen specific, meaning that they will only kill a cell that displays the single antigen they were primed to recognize -a type of T lymphocyte that kills cancer cells -once activated, they divide rapidly and secrete small proteins called cytokines

Internal innate immune system

-when external barriers are breached and pathogens enter the blood and tissues, this system includes barriers that take over with antimicrobial peptides; interferons that prevent viral replication; complement activation (binding of antibodies to the pathogen), inflammation reactions including fever; natural killer cells that attack host cells and harbor intracellular pathogens; and phagocytic cells that engulf and digest extracellular pathogens

Thymus

T cells are born in the bone marrow and released into the bloodstream as immature lymphocytes. Where in the body do they finish maturation?

Breaking down the cell walls of bacteria.

What is the function of lysozyme in the immune system?

Memory T cells are quickly activated to kill cells displaying the viral antigen

Which of the following best describes what occurs when an individual is infected with a viral pathogen two years after receiving a vaccination against that pathogen and does not become ill?

Lymph nodes

Which of the following helps to prevent bacteria from entering the bloodstream? -Capillaries -Pancreas -Lymph nodes -Bone marrow

Antibodies

Which of the following immune system components is NOT part of the innate immune system? -Antibodies -Interferons -Antimicrobial peptides -Lysozyme

Eosinophils

A client is diagnosed with infection by Naegleria fowleri, a parasitic pathogen that infects the brain. An elevation of which of the following immune cells would support the physician's diagnosis?

Infected by new strain of influenza with different surface antigen

An individual receives an influenza vaccine and mounts a very strong immune response, evidenced by a high titer of circulating antibodies. Six weeks after the vaccination, memory B and T cells can be found in circulation. However, six months later, the individual is exposed to influenza and becomes ill. Which of the following best explains why the vaccination appears to have failed?

Although B and T cells are present, antigen-presenting cells fail to activate them.

Bare lymphocyte syndrome accounts for approximately 5% of immunodeficiencies. It is caused by a defect in the MHC protein expressed by macrophages and dendritic cells, resulting in a failure to present antigens. Individuals with this disease cannot effectively fight the infection despite normal B and T cell counts. What is the reason why individuals with this disease are immunocompromised?

B cells produce antibodies that target thyroid cells, and cytotoxic T cells actively kill thyroid cells.

Hashimoto's disease is the most common cause of hypothyroidism in the United States. This autoimmune condition is caused when the immune system attacks and slowly destroys the thyroid gland. Which of the following statements best describes how this condition develops?