LYMPHATIC INTERACTIVE ASSIGNMENT

Which immune cells directly mediate the apoptosis of the kidney cells and therefore the rejection of the kidney itself? (a) Cytotoxic T-cells (b) Dendritic cells (c) Helper T-cells

(a) Cytotoxic T-cells Cytotoxic T-cells mediate apoptosis of infected cells when they recognize foreign antigens presented on MHC Class I molecules. In transplantation, the MHC Class I molecule itself appears differently than the cytotoxic T-cell is used to seeing on the other host patient's cells. The cytotoxic T-cell is tricked into thinking that each cell expressing a foreign MHC Class I molecule is infected. It is important to remember that cytotoxic T-cells are only effective once they have become activated by helper T-cells.

Which of these chemicals aids in inducing apoptosis in a virally-infected cell? (a) Granzyme (b) Histamine (c) Heparin (d) Eicosanoids

(a) Granzyme Granzyme works with perforin to cause apoptosis in virally-infected cells. Perforin creates a small pore in the cell membrane and granzyme enters the cell to induce apoptosis. Eicosanoids, heparin, and histamine are all proinflammatory chemicals that promote the inflammatory response.

Which of the following is NOT an effect of interferons secreted by an infected cell? (a) Interferons attach to viruses, resulting in destruction of the pathogens. (b) Natural killer cells are activated to kill infected cells. (c) Macrophages are stimulated to phagocytose infected cells. (d) Viral replication is inhibited, protecting nearby healthy cells.

(a) Interferons attach to viruses, resulting in destruction of the pathogens. There are three classes of interferons. Interferon-α and -β are secreted by infected cells in response to an infection. These interferons can inhibit viral replication, thereby protecting neighboring cells. They also activate NK cells to kill the infected cells. NK cells, upon activation by interferon-α and -β, secrete interferon-γ to activate nearby macrophages. Viruses are not directly affected by interferons.

Which of these statements is TRUE about macrophages? (a) Macrophages phagocytose bacteria when they recognize complement proteins on the bacterial surface. (b) Macrophages are stimulated to phagocytose bacteria when they are stimulated by IFN-. (c) Macrophages clear antigens from the blood in the classic complement pathway.

(a) Macrophages phagocytose bacteria when they recognize complement proteins on the bacterial surface. Macrophages are important cells in many immune reactions. In the alternative pathway, complement protein C3b helps to activate macrophages for phagocytosis.

Which of these cells or organs plays a role in destroying pathogens using complement? (a) The liver (b) Erythrocytes (c) Macrophages

(a) The liver (b) Erythrocytes (c) Macrophages In the classical complement pathway, complement proteins attach antibody-antigen complexes to erythrocytes. When these erythrocytes pass through the liver, the antibody-antigen complexes are removed. In the alternative pathway, complement protein C3b helps to activate macrophages for phagocytosis. Thus, the liver, erythrocytes, and macrophages are all involved in destroying pathogens using complement.

Would a drug that inhibits the secretion of IL-2 be helpful to prevent transplant rejection? (a) Yes, IL-2 inhibitor drugs would be useful in that they would prevent the activation of cytotoxic T-cells. (b) No, IL-2 inhibitor drugs would accelerate the immune system's rejection of the kidney. (c) Yes, IL-2 inhibitor drugs would be useful in that they would prevent the inflammatory response. (d) No, IL-2 inhibitor drugs would have no effect on transplant rejection.

(a) Yes, IL-2 inhibitor drugs would be useful in that they would prevent the activation of cytotoxic T-cells. Cytotoxic T-cells will eventually kill the cells of the transplanted kidney, but they must first be activated. Helper T-cells activate the cytotoxic T-cells through the use of IL-2. If IL-2 production were inhibited, the cytotoxic mechanism would also be inhibited. This type of drug, however, is so devastating to the immune response that it is not typically used.

Vasodilation and capillary permeability might be helpful in an immune reaction because __________. (a) vasodilation and increased permeability allow immune cells to exit the blood and fight bacteria in the tissues. (b) the resulting tissue swelling pushes bacteria out of the cut. (c) the bacteria have a harder time getting into the bloodstream. (d) vasodilation and increased permeability allow pro-inflammatory chemicals to become concentrated at the site of the infection.

(a) vasodilation and increased permeability allow immune cells to exit the blood and fight bacteria in the tissues. Vasodilation allows for more blood to flow to the infected area, and therefore more of the blood immune cells have exposure to the infected area. The increased capillary permeability allows for these immune cells to exit the blood vessel and access the infected tissue, where they can be useful in fighting the pathogens.

Which of these cell types is capable of producing cytotoxic chemicals against a multicellular parasite? (a) Dendritic cells (b) Eosinophils (c) Mast cells

(b) Eosinophils Eosinophils and basophils are known for their roles in fighting multicellular parasites. Mast cells are tissue-dwelling cells that are often involved in beginning the inflammatory response, and dendritic cells are phagocytic cells often active against bacteria.

Which of the following statements is TRUE regarding fever? (a) Fever is initiated when mast cells release proinflammatory chemicals such as histamine. (b) Fever inhibits bacterial growth and accelerates tissue repair. (c) Fever results in swelling and redness at a locally-infected tissue.

(b) Fever inhibits bacterial growth and accelerates tissue repair. Fevers aid in inhibition of bacterial growth and they help in tissue repair in the body. Although they are uncomfortable to endure, fevers are often useful in speeding up recovery from an infection.

What does a cytotoxic T-cell release upon recognizing a virally-infected cell (assuming the T-cell was previously activated with IL-2)? (a) Histamine (b) Granzymes (c) Eicosanoids (d) Heparin

(b) Granzymes Granzyme works with perforin to cause apoptosis in virally-infected cells. Perforin creates a small pore in the cell membrane, and granzyme enters the cell to induce apoptosis. Eicosanoids, heparin, and histamine are all proinflammatory chemicals that promote the inflammatory response.

Which MHC class molecule is most critical to match for transplant success? (a) MHC Class II (b) MHC Class I

(b) MHC Class I It is most ideal to have matching of both MHC class molecules, but for kidney transplantation, Class I is most critical. The reason is because the cytotoxic T-cells will directly interact with the MHC Class I molecules of the transplanted kidney. It is these molecules that the cells will recognize as foreign.

What portion of T-cell maturation is impaired in APS-1? (a) TCR expression (b) Negative selection (c) Positive selection (d) Cell proliferation

(b) Negative selection T-cells do not proliferate in the thymus. T-cells go through development—the process in which they express their TCR—as well as positive selection in the cortex. We can predict that the cells will not undergo negative selection due to the location clue of the thymus, as well as the functional clue of presenting self-antigens.

Which of the following is FALSE regarding normal flora? (a) Normal flora reside on and in human tissues. (b) Normal flora frequently cause disease. (c) Normal flora include bacteria.

(b) Normal flora frequently cause disease. The term normal flora describes the microbes that live in and on human tissues all the time. We harbor bacteria, fungi, and viruses among our normal flora, but the vast majority are bacteria. Having a healthy and diverse normal flora is important for maintaining health. Normal flora keep pathogens away by outcompeting the pathogens for access to nutrients and space.

The bacterial species that constitute the normal flora of the body differ from one location to another. For example, you will find different bacteria in the large intestine than on the surface of the skin. Which of the following characteristics do you expect that most of the bacterial species found on the skin share? (a) The bacterial species have a specific temperature requirement. (b) The bacterial species can tolerate slightly acidic environments. (c) The bacterial species require a very moist environment.

(b) The bacterial species can tolerate slightly acidic environments. Bacteria found on the skin can generally tolerate drier and more acidic environments than the bacteria found on internal surfaces. Both the skin secretions, sebum and sweat, are slightly acidic. Therefore, only bacteria that can tolerate acidic environments can survive on the skin.

Which of the following types of pathogens is NOT cellular, and therefore does not have cellular structures such as ribosomes? (a) All of these pathogen types are cells, or are made up of cells. (b) Viruses (c) Parasites (d) Bacteria

(b) Viruses Viruses are not cells. They lack any organelles and they cannot replicate themselves. Many types of viruses even lack a cell membrane. Bacteria are cells, although they do not look like human cells. Bacteria are prokaryotic cells; they lack a nucleus and membrane-bound organelles, but they have ribosomes and can undergo replication. Parasites are multicellular, so they have more than one cell. Their cells are eukaryotic.

Fc regions are similar from one patient to another. Would phagocytic cells be involved in clearing the Ebola virus from the patient recipient? (a) No, phagocytic cells of the recipient patient would not recognize or be capable of binding the transplanted antibodies. (b) Yes, opsonization of the neutralized viruses is likely to occur.

(b) Yes, opsonization of the neutralized viruses is likely to occur. Because Fc receptors are universal, the phagocytes of the recipient patient will recognize the transplanted antibodies and phagocytose the virus-antibody complex. This will lead to immune activation in the host.

Where are protective epithelial surfaces found? (a) Mucous membranes only (b) The cutaneous membrane only (c) All external and internal surfaces of the body

(c) All external and internal surfaces of the body Epithelial surfaces line every external and internal structure of the human body. The epithelial surfaces form tight boundaries, and also have secretions such as mucus and sweat that add additional antimicrobial properties.

Over thirty different proteins and protein fragments are involved in the complement pathways; each protein serves a specific purpose. There are two main complement pathways—the classical pathway and the alternative pathway. In the classical pathway, blood plasma complement proteins interact with antibodies from the adaptive immune response to help clear pathogens from the blood. In the alternative pathway, complement proteins bind directly to pathogens to destroy them directly, or cause them to be phagocytosed. In searching through data from a popular ancestry website, a group of scientists noticed that there is a common homozygous mutation (meaning a mutation on both copies of the gene) called p.A252T homozygous. This mutation is within the gene for complement C5. This mutation can be found in individuals of African descent at a frequency of about 1 out of every 1,100 people. The individuals with this mutation have very low circulating levels of complement protein C5b in their bloodstreams. What clinical symptoms do you expect from patients with p.A252T homozygous mutations? (a) Frequent immune reactions where their immune system attacks healthy cells (b) A decrease in frequency of colds and other illnesses caused by viruses (c) An increase in frequency of bacterial diseases such as meningitis and pneumonia (d) A buildup of immune products in the liver

(c) An increase in frequency of bacterial diseases such as meningitis and pneumonia Because individuals with the p.A252T homozygous mutation have lost one of their defenses against bacteria, these individuals are more at risk of bacterial illnesses. In fact, this mutation, which is relatively common in Southern Africa, has been found in much higher frequency among patients suffering from bacterial meningitis.

Over thirty different proteins and protein fragments are involved in the complement pathways; each protein serves a specific purpose. There are two main complement pathways—the classical pathway and the alternative pathway. In the classical pathway, blood plasma complement proteins interact with antibodies from the adaptive immune response to help clear pathogens from the blood. In the alternative pathway, complement proteins bind directly to pathogens to destroy them directly, or cause them to be phagocytosed. In searching through data from a popular ancestry website, a group of scientists noticed that there is a common homozygous mutation (meaning a mutation on both copies of the gene) called p.A252T homozygous. This mutation is within the gene for complement C5. This mutation can be found in individuals of African descent at a frequency of about 1 out of every 1,100 people. The individuals with this mutation have very low circulating levels of complement protein C5b in their bloodstreams. Which of the following best describes the role of complement protein C5b in the immune response? multiple choice 1 (a) C5b helps clear bacteria from the bloodstream via the liver. (b) C5b helps tag bacteria for phagocytosis. (c) C5b helps form a complement protein complex on bacteria cells that leads to their destruction.

(c) C5b helps form a complement protein complex on bacteria cells that leads to their destruction. The formation of C5b is the first step in the formation of the MAC complex. This is a composite of complement proteins that forms on the surface of a bacterial cell, forming a pore in the bacterial cell wall. This pore allows water to move across the membrane; in general, water will enter the cell and lead to the bursting of the bacterial cell, called cytolysis.

Which of these cells is capable of phagocytosis? (a) NK cells (b) Red blood cells (c) Dendritic cells (d) Mast cells

(c) Dendritic cells Dendritic cells and macrophages are the two most common types of phagocytic cells. These cells, also called antigen-presenting cells, are able to present pieces of the pathogens they phagocytose to the immune system, and play a central role in immune system activation.

Which of the following may have occurred in the Ebola patients after the blood plasma and antibody transfusion? (a) Ebola viruses will precipitate after being bound by multiple antibodies. (b) Ebola viruses will agglutinate, forming large clumps that can clog capillaries. (c) Ebola viruses will be neutralized as they become coated with antibodies.

(c) Ebola viruses will be neutralized as they become coated with antibodies. The antigens of Ebola would be found on the viral surface as well as inside of cells. Free virus could be neutralized by Ebola-antigen-specific antibodies, rendering these virus particles unable to cause infection. Agglutination would not occur because viruses are not cells and the host cells would not express Ebola antigens on their surface except bound to MHC molecules. Because Ebola does not release toxins or other soluble antigens, precipitation would not occur.

Which of these cells produces IL-2? (a) Cytotoxic T-cells (b) Both types of T-cells (c) Helper T-cells

(c) Helper T-cells Dendritic cells and macrophages are the two most common types of phagocytic cells. These cells, also called antigen-presenting cells, are able to present pieces of the pathogens they phagocytose to the immune system and play a central role in immune system activation.

Which of the following is largely responsible for swelling during inflammation? (a) Heparin (b) Eicosanoids (c) Histamine

(c) Histamine As the capillary permeability increases, an increased amount of fluid from the blood leaks out of the capillary and into the tissues. As more liquid builds up in the tissues, swelling becomes noticeable. Histamine is a major contributor to vascular permeability.

Rare genetic mutations can compromise the expression of CAMs. In these cases, what symptoms might be most likely? (a) Overactive immune responses where the immune cells attack healthy tissues (b) A decrease in the amount of time to recover from an infection (c) Persistent infections, or trouble healing from infections that wouldn't be serious in other patients

(c) Persistent infections, or trouble healing from infections that wouldn't be serious in other patients In diseases caused by CAM mutations, the process of margination is sometimes compromised. In these patients, fewer leukocytes can reach the site of infection, allowing the infection to last longer and sometimes grow more serious than it would have in a patient without the mutation.

Which of these molecules is likely to be presented from the endogenous pathway? (a) Lipopolysaccharide from a phagocytosed bacterium (b) All of these are likely to be presented from the endogenous pathway. (c) Viral capsid protein (d) Cellular waste antigens from phagocytosis of neutrophil waste

(c) Viral capsid protein The endogenous pathway is a pathway through which a non-phagocytic cell can express antigen via MHC Class I. Cells do this all the time, and when they are not infected with viruses, they express self-antigen, which does not elicit an immune response. However, when a cell is infected with a virus, viral proteins will be expressed via this endogenous pathway and gain the attention of the immune system.

The T-cells of patients with AIRE could have which of the following problems? (a) The T-cells will express a mutated form of the TCR (b) The T-cells will not express the CD4+ receptor (c) The T-cells will not express the CD8+ receptor (d) The T-cells will express all the correct receptors, but may react with self-antigens.

(d) The T-cells will express all the correct receptors, but may react with self-antigens. If the T-cells are not negatively selected based on their interaction with self-antigens, then they are released with the chance that they would react against self-antigen.

EXUDATE

A collective substance of immune cells, plasma proteins, and fluids from the blood plasma that moves into damaged tissue. This substance washes the infected area and is picked up by the lymphatic capillaries to form lymph, which travels to lmph nodes for cleansing.

PHAGOCYTIC CELLS

A variety of cells such as macrophages, dendritic cells, and neutrophils engulf and destroy infectious agents though phagocytosis. Some of these phagocytic cells, including macrophages and dendritic cells, undergo a specialized process of displaying these captured foreign antigens, called antigen presentation. Antigen presentation links innate immunity to the adaptive branch of immunity.

EBOLA VIRUS

A virus that is transmitted through exchange of blood and other bodily fluids. Once the virus enters the body it resides inside of cells. During the Ebola outbreak of 2014-2015 there were no available vaccines or medications. Several patients were saved, however, by receiving blood plasma containing antibodies from patients who had been previously infected and survived.

B-cell receptors

B-cells develop unique B-cell receptors (BCR) through DNA shuffling process called recombination. The BCR is a Y-shaped membrane immunoglobulin (Ig) molecule capable of binding a specific antigenic determinant, or epitope, through its antigen binding site. Thousands of identical BCRs are expressed on each B-cell membrane. These B-cells go through this development process in the red bone marrow.

RED BONE MARROW

B-cells remain here throughout the maturation process. Pre-T-cells exit the red bone marrow.

____________ enter the tissues through a cut or puncture.

Bacteria

PROINFLAMMATORY SECRETING CELLS

Both circulating basophils and tissue-residing mast cells release proinflammatory chemicals that initiate and enhance inflammation. Eicosanoids promote the overall inflammatory process, histamine acts as a vasodilator and increases capillary permeability, and heparin is an anticoagulant.

EPITHELIAL SURFACES

Both external and internal epithelial surfaces create physical barriers. The external cutaneous membrane of the skin and the internal mucous membrane surfaces create a boundary to block pathogens from entering the body.

THYMIC SELECTION OUTCOME

CD4+ and CD8+ thymocytes that complete thymic selection become either cytotoxic T-cells or helper T-cells through selective loss of either their CD4 or CD8 proteins. T-cells capable of binding MCH class I proteins become naive cytotoxic T-cells. while T-cells capable of binding MHC class II proteins become naive helper T-cells.

KIDNEY TRANSPLANT

Can be required when a patient has sustained extensive damage to a kidney through injury or disease. When a patient needs a kidney transplant, the team of transplant doctors searches for an available kidney that expresses a very similar major histocompatibility complex (MHC) to the host patient. MHC matching is essential to the long-term health of the transplanted kidney. Once the kidney is transplanted, the kidney cells interact with the cells of the immune system. If the MHC molecules expressed on the transplanted kidney cells are too different from the host MHC molecules, the immune cells can confuse them with MHC molecules carrying foreign antigens. An immune reaction can result in which the cells of the transplanted kidney die by apoptosis. This process, called transplant rejection, will eventually compromise the transplanted kidney and a new kidney will need to be found.

DIAPEDESIS STEP 2

Cell adhesion molecules allow leukocytes to adhere to blood vessel walls and come to a stop.

DIAPEDESIS STEP 1

Cell adhesion molecules bind to leukocytes and help them slow near the location of the infection.

MARGINATION

Cell-adhesion molecules (CAMS) present on leukocytes bind to exposed CAMS found on the capillary walls of injured tissues.

CHEMOTAXIS

Cells follow chemicals signals to the site of damage

CLASSICAL PATHWAY

Complement binds to and facilitates the elimination of an antigen-antibody complex by attaching the complex to an erythrocyte and delivering it to the liver or spleen. Here, macrophages strip immune complexes from the erythrocyte.

Where in the thymus do thymocytes begin their maturation process?

Cortex

PATHOGENS

Disease-causing agents and can be viruses, bacteria, protozoans, fungi, or multicellular parasites.

THYMOCYTE

Each thymocyte expresses a unique epitope-specific T-cell receptor (TCR) and both CD4 and CD8 cell-docking proteins. These cells, which are now referred to as CD4+ and CD8+ cells, undergo further testing as they develop, referred to as positive and negative selection.

PARASITE-DESTROYING CELLS

Eosinophils play a variety of roles in innate immunity, but specialize in attacking multicellular parasites. These cells locate and destroy parasitic worms by releasing large amounts of cytotoxic chemicals.

MHC CLASS 1 PROTEINS

Expressed on the surface of most cells of the body such as skin cells, liver cells, and others. Should a cell become infected with a virus, viral antigens are processed in the cells and expressed on the cell surface within the MHC class I molecule. Cytotoxic T-cells, expressing their T-cell receptor and CD8 molecule, can recognize this viral particle within the MHC class I and, if the cytotoxic T-cell has been activated by IL-2, the cytotoxic T-cell will react by releasing granzymes and perforin. The release of granzymes and perforin has the effect of killing the virally-infected cell and preventing the spread of infection further.

MHC CLASS 2 PROTEINS

Expressed only on the surface of antigen-presenting cells such as macrophages. When macrophages phagocytose pathogens or antigens from the extracellular fluid, the macrophages display the antigens on the surface of their cells using MHC Class II. A helper T-cell that expresses its T-cell receptor and CD4 molecule can recognize this antigen. The helper T-cell will react by releasing IL-2 into the extracellular fluid. This IL-2 can activate both the helper T-cell as well as nearby cytotoxic T-cells. The helper T-cell will proliferate in response.

PYROGENS

Fever-inducing molecules secreted into the bloodstream. Exogenous pyrogens are secreted by pathogens such as bacteria, and endogenous pyrogens are secreted by immune cells. Pyrogens travel through the bloodstream, triggering a cascade of events that stimulates the hypothalamus to increase body temperature. Fevers aid the immune system by inhibiting microbial growth and enhancing tissue repair.

COMPLEMENT (Antimicrobial protein)

Found in the blood plasma, react strongly to bacteria. (in the blood plasma) Become activated by the presence of a pathogen through either the classical or alternative pathway.

LYMPH NODES/ VESSELS

Fully developed B-and T-cells aggregate in secondary lymphatic structures, where they are likely to encounter immune challenges.

INFLAMMATORY RESPONSE

Inflammation is an immediate, innate response to an injury or immune challenge. This multi-step process begins with the release of a variety of proinflammatory chemicals, such as histamine, from injured tissue, immune cells, and infectious organisms. This triggers vasodilation, increased capillary permeability, and recruitment of immune cells.

DIAPEDESIS STEP 3

Leukocytes exit the blood vessel in the process of diapedesis.

DIAPEDESIS

Leukocytes move out of blood, and into the tissue.

DIAPEDESIS STEP 4

Leukocytes travel to the infected area by chemotaxis to fight the infection.

Where in the thymus do thymocytes complete their development?

Medulla

MEMBRANE ATTACK COMPLEX

Multiple complement proteins work together to directly interact with, and kill, pathogens. The formation of specific complement protein, C5b, triggers additional complement proteins to form a membrane attack complex (MAC). The MAC creates openings that breach the pathogen cells wall, inducing cytolysis.

APOPTOSIS-INITIATING CELLS

Natural killer (NK) cells play an important role in searching out and destroying a variety of unwanted cells in the body, including damaged, infected, tumor, and transplanted cells. Once activated, NK cells release an arsenal of cytotoxic chemicals-perforins and granzymes. Together these chemicals destroy unhealthy target cells by puncturing their membrane and inducing apoptosis.

NORMAL FLORA

Not all microorganisms are harmful. Multiple types of nonpathogenic, harmless bacteria reside on, and in, the skin and mucosal membranes. Those microbes play a role in innate immunity by acting as a biological shield, suppressing and outcompeting pathogenic bacteria within these tissues.

CELLS OF INNATE IMMUNITY

Pathogens that breach the first line of defense encounter an army of nonspecific cells that contribute to the second line of defense in innate immunity. These cells have an immediate, generalized response to each challenge, regardless of previous exposure.

POSITIVE SELECTION

Positive selections tests CD4+ and CD8+ thymocytes to determine if they bind to major histocompatibility complex (MHC) class I or MHC class II molecules, displayed on thymic epithelial cells. Thymocytes with either CD8 proteins that bind MHC Class I, or CD4 proteins that bind MHC Class II, survive this process and continue to negative selection. Positive selection occurs in the cortex region of the thymus.

HEART/ BLOOD VESSELS

Pre-T-cells exit the red bone marrow and travel to the thymus through blood vessels. Mature B-cells travel through the blood vessels to secondary lymphatic organs, such as lymph nodes.

____________ are released by damaged and infected tissues.

Proinflammatory chemicals

ANTIBODIES

Proteins made by the immune system that are exquisitely specific to antigens. Within a single human there are many different antibodies specific to a wide variety of antigens from different pathogens. Antibodies accomplish a few different immune reactions. Alone, antibodies can coat and disable pathogens. The antibodies also have a region that does not bind antigen, known as the Fc region. This region is recognized by immune cells and proteins, and aids in the destruction of the pathogen/antigen. Antibodies can be found free-floating in the plasma, or can be expressed on the surface of B-cells. In both cases, antibodies can bind antigen. When B-cell-bound antibodies bind antigen, they initiate a series of steps that result in activation of the B-cell. These activated B-cells proliferate into memory B-cells and plasma cells capable of producing large quantities of soluble (free-floating) antibodies specific to the antigen.

INTERFERON (Antimicrobial protein)

Proteins secreted from activated cells, are especially effective against viruses. Group of immune-stimulating, anti-viral cytokines. Virus-infected cells secret IFN-alpha and IFN-beta. These IFNs protect healthy cells from infection by interrupting the viral replication process. Additionally, IFN-alpha and IFN-beta stimulate NK cells to both destroy infected cells and release IFN-gamma, which stimulates phagocytosis of the infected cell by macrophages.

Which of these processes involves a phagocytic cell? (a) Opsonization (b) Agglutination (c) Neutralization (d) Precipitation

SECOND LINE OF DEFENSE Free antigen binds to B-cell receptor (BCR). Antigen is presented on MHC Class II molecule on B-cell surface. TCR and CD4 molecules on the surface of a helper T-cell interact with MHC Class II molecule expressing antigen. Helper T-cell secretes IL-4. B-cell is activated and begins to proliferate. Memory B-cells and plasma cells are produced. (a) Opsonization Neutralization describes the coating of a pathogen or antigen with antibodies. Agglutination describes the binding together of cells by antibodies. Precipitation is the binding together, cross-linking, of soluble antigens. Opsonization involves the phagocytosis of a neutralized pathogen by a phagocytic cell.

SECRETION WITH ITS COMPONENTS

SWEAT Acidic secretion - sweat Dermicidin Lysozymes Defensins MUCUS Lysozymes Defensins Antibodies SEBUM Acidic secretion - Sebum

SWEAT GLAND (Skin)

Salty, acidic secretion that contains a variety of antimicrobial compounds including lysozymes, defensins, and dermicidin.

GOBLET CELL (Mucosal membrane)

Secret a hydrated form of mucin, called mucus, which contains lysozyme, defensins, and IgA antibodies that adhere to infectious agents.

SEBACEOUS GLAND (Skin)

Secret an oily substance called sebum.

SEBUM

Slightly acidic complex mixture that includes glycerides, free fatty acids, and cholesterol.

OPSONIZATION

Specific complement proteins within the blood can bin directly to a pathogen's cell wall upon exposure. This process assist in the removal of these pathogens because complement-bound pathogens are much more likely to be phagocytized than unbound pathogens.

LYMPHATIC ORGANS WITH CELL TYPE

T-CELL Thymus CD4 CD8 B-CELL BCR Immunoglobulin B-CELL & T-CELL Lymph nodes Bone marrow T-cells and B-cells are both formed in the bone marrow. B-cells express a cell surface receptor, known as the B-cell receptor or BCR. Later in B-cell maturation, they secrete immunoglobulins. T-cells leave the bone marrow at an early stage in their development and finish developing in the thymus. Here they express either a CD4 or CD8 receptor. Mature T-cells and B-cells gather in the lymph nodes, where they become activated during infections.

THYMUS

T-cells complete their development here.

INFECTIOUS AGENTS

The human body encounters pathogens regularly, including varieties of viruses, bacteria, multicellular parasites, fungi, protozoans. The body's general defenses against these pathogens are collectively referred to as innate immunity.

INNATE IMMUNE SYSTEM

The innate immune system acts broadly against any pathogen, even if the body has never encountered that pathogen before. One feature of innate immune cells such as macrophages and dendritic cells is that they are able to clear bacteria by phagocytosis. Many cells of the innate immune system secrete chemicals that aid in the immune response. Some cells of the innate immune system can directly kill pathogen-infected cells by using chemicals that punch holes in their membranes. Other innate immune cells can use chemicals to directly disable or kill multicellular parasites.

SECRETIONS

The skin and mucosal membranes produce a variety of substances that contribute to the overall effectiveness of the pathogen barrier. The acidic secretions of the skin contain multiple antibacterial and antifungal substances. The mucosal membranes, found in places such as respiratory, digestive, and reproductive tracts, produce thick antimicrobial secretions that trap and destroy microbes.

NEGATIVE SELECTION

Thymocytes that survive positive selection migrate to the medullary region of the thymus, where they undergo negative selection. Negative selection tests the ability of CD4+ and CD8+ thymocytes to tolerate self-antigens. During this process, thymic dendritic cells display self-antigens on MHC complexes. Thymocytes that bind self-antigens with their TCRs are destroyed, while surviving thymocytes continue maturing.

Capillaries ____________ , causing fluid and plasma proteins to leave the blood and enter the tissues.

become more permeable

LYMPHOCYTE FORMATION STEP 1 Pre-T-cells form when stem cells undergo replication in the ____________ .

bone marrow

Neutrophils migrate to the site of infection by ____________ , where they can fight the infection.

chemotaxis

LYMPHOCYTE FORMATION STEP 3 In the thymus ____________ , T-cells begin their maturation process.

cortex

Neutrophils exit the bloodstream by the process of ____________ .

diapedesis

Local blood vessels ____________ , causing increased blood flow to the area.

dilate

LYMPHOCYTE FORMATION STEP 5 Pre-T-cells undergo ____________ , the process by which the cell is checked for reactivity against self-antigens in the thymus ____________ .

negative selection; medulla

LYMPHOCYTE FORMATION STEP 4 Pre-T-cells undergo ____________ , the process by which they make sure their TCR is reactive, in the thymus cortex.

positive selective

AUTOIMMUNE POLYENDOCRINOPATHY SYNDROM TYPE 1 (ASP-1)

rare autoimmune disorder. Autoimmune diseases occur when the immune system attacks the cells of the body as if they were pathogens. In APS-1, a protein called AIRE, expressed in the thymus, is mutated. AIRE protein is part of the apparatus that presents self-antigens to T-cells in the medulla of the thymus. In APS-1, AIRE protein is mutated to the extent that it cannot perform its function.

LYMPHOCYTE FORMATION STEP 2 Pre-T-cells travel in the blood to get to the ____________ .

thymus