Immune System

complement cascade

1. opsonization 2. chemotaxis 3. cell lysis 4. agglutination

phagocytes

A type of white blood cell that ingests invading microbes

Recognition of self vs. non-self by the adaptive immune system in humans is accomplished in which of the following ways? A. Exposure of T cells to the body's own antigens in the thymus B. Exposure of B cells to the body's own antigens in the thymus C. Exposure of T cells to the body's own antigens in the bursa of Fabricius D. Exposure of B cells to the body's own antigens in the bursa of Fabricius

A. Exposure of T cells to the body's own antigens in the thymus The thymus is an organ in humans where T-cells mature C and D are wrong because the bursa of Fabricius is an organ found in birds; B-cells were originally found in this organ

Monocytes move from the systemic circulatory system into general connective tissues, where they differentiate into what phagocytic cell type? A. macrophage B. B cell C. neutrophil D. T cell

A. macrophage

Which portion of an antibody provides antigen-binding sites? A. variable portion B. light chain C. constant portion D. heavy chain

A. variable portion Both the heavy chains and light chains of antibodies are split into a constant region and a variable portion The variable portions of an antibody provide antigen-binding sites

B cells

After formation and maturation in the bone marrow (hence the name "B cell"), the naive B cells move into the lymphatic system to circulate throughout the body. In the lymphatic system, naive B cells encounter an antigen, which starts the maturation process for the B cell. B cells each have one of millions of distinctive surface antigen-specific receptors that are inherent to the organism's DNA.

Myelogenous leukemias are caused by the cancerous production of innate (non-specific) immune system cells: in which tissue is such production most likely to occur? A. thymus B. bone marrow C. spleen D. lymph nodes

B. bone marrow The bone marrow is the main reservoir of hematopoietic stem cells. A is wrong because the thymus is a site of maturation of T-cells, which are part of the adaptive immune system.

Major histocompatibility complex (MHC) refers to a large group of genes that code for proteins that play an essential role in which of the following? A. Phagocytosis by macrophages B. Antigen presentation to B lymphocytes C. Antigen presentation to T lymphocytes D. Phagocytosis by neutrophils

C. Antigen presentation to T lymphocytes MHC genes code for cell surface proteins that play a critical role in antigen presentation Antigen presenting cells present their antigens to various types of T cells

Central tolerance refers to which of the following processes? A. Destruction of lymphocytes that are not specific for self-antigens B. Destruction of self-antigens that are specific for lymphocytes C. Destruction of lymphocytes that are specific for self-antigens D. Production of self-antigens that are specific for lymphocytes

C. Destruction of lymphocytes that are specific for self-antigens Central tolerance is the process whereby the body destroys immune cells that are reactive with antigens present on the bodies own cells. "Self-antigens" are the antigens derived from the bodies own cells.

Humoral immunity is a type of adaptive immunity that results in the circulation of which of the following throughout the blood? A. antigens B. natural killer cells C. antibodies D. macrophages

C. antibodies

In the developing fetus, prenatal hematopoiesis (the differentiation and development of immune cells) is not generally known to occur in which of the following organs? A. liver B. lymph nodes C. appendix D. spleen

C. appendix

Which of the following cell types of the innate immune system does not perform phagocytosis? A. macrophages B. eosinophils C. basophils D. neutrophils

C. basophils Basophils release histamine, a vasodilator that is commonly used by the body to respond to allergens.

Which of the following is not one of the three main antigen-presenting cell types? A. macrophages B. dendritic cells C. B lymphocytes D. natural killer cells

D. natural killer cells Natural killer cells, part of the innate immune system, secrete cytotoxic chemicals meant to destroy bacteria, cells infected by a virus, tumor cells, etc. A and B are wrong because macrophages and dendritic cells play an important role as antigen-presenting cell types C is wrong because B-cells are mainly known as antibody producing cells, but they also can play a role as antigen-presenting cells

antigens

Foreign material that invades the body; causes an immune reponse

innate immunity

Immunity that is present before exposure and effective from birth. Responds to a broad range of pathogens.

major cells types of innate immunity

Macrophages, Neutrophils, Natural Killer Cells, Dendritic Cells, Basophils, Eosinophils

Natural killer cells

Natural Killer cells (NK cells), do not attack pathogens directly. Instead, natural killer cells destroy infected host cells in order to stop the spread of an infection. Infected or compromised host cells can signal natural kill cells for destruction through the expression of specific receptors and antigen presentation.

negative selection of T cells

Negative selection tests for self tolerance. Negative selection tests the binding capabilities of CD4 and CD8 specifically. The ideal example of self tolerance is when a T cell will only bind to self-MHC molecules presenting a foreign antigen. If a T cell binds, via CD4 or CD8, a self-MHC molecule that isn't presenting an antigen, or a self-MHC molecule that presenting a self-antigen, it will fail negative selection and be eliminated by apoptosis.

T cells

Once formed in the bone marrow, T progenitor cells migrate to the thymus (hence the name "T cell") to mature and become T cells. While in the thymus, the developing T cells start to express T cell receptors (TCRs) and other receptors called CD4 and CD8 receptors. All T cells express T cell receptors, and either CD4 or CD8, not both. So, some T cells will express CD4, and others will express CD8.

major cells types of adaptive immunity

T cells, B cells

B cell receptor

The antigen receptor on B cells: a Y-Shaped, membrane-bound molecule consisting of two identical heavy chains and two identical light chains linked by disulfide bridges and containing two antigen-binding sites.

innate immune system

The innate immune system is always general, or nonspecific, meaning anything that is identified as foreign or non-self is a target for the innate immune response. The innate immune system is activated by the presence of antigens and their chemical properties.

the complement system

a mechanism that complements other aspects of the immune response. Typically, the complement system acts as a part of the innate immune system, but it can work with the adaptive immune system if necessary. made of a variety of proteins that, when inactive, circulate in the blood. When activated, these proteins come together to initiate the complement cascade

opsonization

a process in which foreign particles are marked for phagocytosis. All of the pathways require an antigen to signal that there is a threat present. Opsonization tags infected cells and identifies circulating pathogens expressing the same antigens.

chemokines

a type of cytokines that are released by infected cells. Infected host cells release chemokines in order to initiate an immune response, and to warn neighboring cells of the threat

key components of adaptive

antibodies

dendritic cells

antigen-presenting cells that are located in tissues, and can contact external environments through the skin, the inner mucosal lining of the nose, lungs, stomach, and intestines. Since dendritic cells are located in tissues that are common points for initial infection, they can identify threats and act as messengers for the rest of the immune system by antigen presentation. Dendritic cells also act as bridge between the innate immune system and the adaptive immune system.

key components of innate immunity

antimicrobial peptides and proteins, such as toxic granules

cell-mediated immunity

can be acquired through T cells from someone who is immune to the target disease or infection. "Cell-mediated" refers to the fact that the response is carried out by cytotoxic cells. Much like humoral immunity, someone who has not been exposed to a specific disease can gain cell-mediated immunity through the administration of Th and Tc cells from someone that has been exposed, and survived the same disease. The Th cells act to activate other immune cells, while the Tc cells assist with the elimination of pathogens and infected host cells.

positive selection of T cells

ensures MHC restriction by testing the ability of MHCI and MHCII to distinguish between self and nonself proteins. In order to pass the positive selection process, cells must be capable of binding only self-MHC molecules. If these cells bind nonself molecules instead of self-MHC molecules, they fail the positive selection process and are eliminated by apoptosis.

T regulatory cells

express CD4 and another receptor, called CD25. T regulatory cells help distinguish between self and nonself molecules, and by doing so, reduce the risk of autoimmune diseases.

helper T cells

express CD4, and help with the activation of Tc cells, B cells, and other immune cells.

cytotoxic T cells

express CD8, and are responsible for removing pathogens and infected host cells.

mast cells

found in mucous membranes and connective tissues, and are important for wound healing and defense against pathogens via the inflammatory response. they release cytokines and granules that contain chemical molecules to create an inflammatory cascade.

basophils

granulocytes that attack multicellular parasites. Basophils release histamine, much like mast cells. The use of histamine makes basophils and mast cells key players in mounting an allergic response.

eosinophils

granulocytes that target multicellular parasites. Eosinophils secrete a range of highly toxic proteins and free radicals that kill bacteria and parasites. The use of toxic proteins and free radicals also causes tissue damage during allergic reactions, so activation and toxin release by eosinophils is highly regulated to prevent any unnecessary tissue damage.

self vs. nonself discrimination innate vs. adaptive immunity

innate: Innate immunity is based on self vs. nonself discrimination, so it has to be perfect adaptive: Not as good as the innate immune system, but still pretty good at determining which is which. Problems in self vs. nonself discrimination result in autoimmune diseases

diversity and customization of innate vs. adaptive immunity

innate: Limited - Receptors used are standard and only recognize antigen patterns. No new receptors are made to adapt the immune response adaptive: Highly diverse - can be customized by genetic recombination to recognize epitopes and antigenic determinants.

response times of innate vs adaptive immunity

innate: fast (minutes or hours) adaptive: slow (days)

immunological memory of innate vs. adaptive immunity

innate: none adaptive: memory used can lead to faster response to recurrent or subsequent infections

specificity of innate vs. adaptive immunity

innate: only specific for molecules and molecular patterns associated with general pathogens or foreign particles adaptive: highly specific! Can discriminate between pathogen vs. non-pathogen structures, and miniscule differences in molecular structures

MHC molecules

membrane-bound surface receptors on antigen-presenting cells, like dendritic cells and macrophages. CD4 and CD8 play a role in T cell recognition and activation by binding to either MHCI or MHCII.

humoral immunity

mmunity from serum antibodies produced by plasma cells. More specifically, someone who has never been exposed to a specific disease can gain humoral immunity through administration of antibodies from someone who has been exposed, and survived the same disease. "Humoral" refers to the bodily fluids where these free-floating serum antibodies bind to antigens and assist with elimination.

cytokines

molecules that are used for cell signaling, or cell-to-cell communication; used to trigger cell trafficking, or movement, to a specific area of the body

neutrophils

phagocytic cells that are also classified as granulocytes because they contain granules in their cytoplasm. These granules are very toxic to bacteria and fungi, and cause them to stop proliferating or die on contact.

effector B cell

plasma cell

central tolerance

process whereby the body destroys immune cells that are reactive with antigens present on the bodies own cells.

adaptive immunity

the ability to recognize and remember specific antigens and mount an attack on them

chemotaxis

the attraction and movement of macrophages to a chemical signal. Chemotaxis uses cytokines and chemokines to attract macrophages and neutrophils to the site of infection, ensuring that pathogens in the area will be destroyed. By bringing immune cells to an area with identified pathogens, it improves the likelihood that the threats will be destroyed and the infection will be treated.

cell lysis

the breaking down or destruction of the membrane of a cell. The proteins of the complement system puncture the membranes of foreign cells, destroying the integrity of the pathogen. Destroying the membrane of foreign cells or pathogens weakens their ability to proliferate, and helps to stop the spread of infection.

macrophages

type of phagocyte; leave the circulatory system by moving across the walls of capillary vessels. The ability to roam outside of the circulatory system is important, because it allows macrophages to hunt pathogens with less limits. Macrophages can also release cytokines in order to signal and recruit other cells to an area with pathogens.

agglutination

uses antibodies to cluster and bind pathogens together, much like a cowboy rounds up his cattle. By bringing as many pathogens together in the same area, the cells of the immune system can mount an attack and weaken the infection.

leukocytes

white blood cells