Chapter 26 Study Guide Questions

What term is used to describe the unique molecules found on the surface of different pathogens?

antigens

Where do all blood cells originate? What determines what they differentiate into?

bone marrow (Hematopoietic stem cells reside in the bone marrow and have the unique ability to differentiate into all mature blood cell types); differentiation occurs based upon which lymphoid organ the cells mature in

a group of sequentially interacting plasma proteins, many with enzymatic activity, that functions to boost efficiency of both innate and adaptive immune responses for the destruction of pathogens

complement

when complement proteins bind in a series to the cell to form a membrane attack complex that pokes holes in the cell

complement pathway

Describe the relative importance of innate immunity compared to adaptive immunity. Is one more important than the other?

innate: includes natural barriers and inflammation; forms first line of defense adaptive: slow and specific process; involves "memory" Neither more important

What are MHCs and why are they important?

major histocompatibility complex > proteins found on host cell surfaces MHC1: all nucleated cells MHC2: antigen presenting cells (b cells, macrophages, dendritic cells) MHC molecules are important components of the immune system because they allow T lymphocytes to detect cells, such as macrophages, that have ingested infectious microorganisms. In uninfected healthy cells, the MHC molecule presents peptides from its own cell (self peptides), to which T cells do not normally react.

How does opsonization help fight bacterial infections?

neutralizes pathogens and makes them more likely to be identified, engulfed, and destroyed by phagocytes the bacteria is covered by serum proteins (complement) and antibodies (signals for cell lysis)

Can we survive in a normal environment without immunity?

no

Is the coating of pathogens with host immune proteins, such as antibodies or C3b, resulting in enhanced phagocytosis of target cells.

opsonization

Under what conditions are interferons produced, and how do they limit the transmission of viruses from one host cell to another?

produced by virally infected cells; serve as a warning and stimulates production of antiviral proteins in unaffected cells when they receive the signal from infected cells

Identify the major symptoms of localized inflammation.

redness, swelling, pain, and heat usually located at the site of the infection or injury

What other factors may control the outcome of an infectious disease?

-Amyloid-B (AB): may play a role in innate defense of the brain by containing invading pathogens. AB proteins form a mesh of fibrils to trap bacteria that are able to invade the CNS. -Sebaceous Glands in the skin: secrete fatty acids and lactic acid, lowering the acidity of the skin to pH 5 and inhibiting colonization by many pathogenic bacteria -Established Normal Microbiota -Defensins: antibacterial substance that enhances resistance to infection and invasion -Lumen of the Kidney, the Eye, the Respiratory System, and the Cervical Mucosa: constantly bathed with tears, mucus and or other secretions that contain lysozyme which is an enzyme that can kill bacteria by digesting the cell wall. -Host Hygiene -Adaptive Immunity

Identify the major symptoms of septic shock.

-low blood pressure (hypotension) that makes you feel dizzy when you stand up. -a change in your mental state, such as confusion or disorientation. -diarrhoea. -nausea and vomiting. -cold, clammy and pale skin. -death

Describe several reasons why phagocytes are not always effective at removing pathogens from the body.

Capsules: capsule prevents necessary molecular interactions between the surface of the phagocyte and that of the bacterial cell, encapsulated are often highly resistant to phagocytosis Leukocidins: phagocyte-killing proteins... releases the pathogen unharmed... kill white blood cells. Dead white blood cells are found in pus. Carotenoids: neutralize singlet oxygen and prevent pathogen killing...has a waxy cell wall that absorbs free radicals. This pathogen lives and divides within phagocytes.

How might the physical and chemical barriers to pathogens be compromised?

Despite these barriers, pathogens may enter the body through skin abrasions or punctures, or by collecting on mucosal surfaces in large numbers that overcome the mucus or cilia. Some pathogens have evolved specific mechanisms that allow them to overcome physical and chemical barriers.

What defects in the phagocyte might cause lack of phagocytosis?

First, the phagosome must fuse with the lysosome. This process is enabled by microtubules, which facilitate the movement of organelles within cells. > Defective microtubule function would likely prevent the formation of phagolysosomes. Chediak-Higashi is a disease characterized by defective microtubule function and impaired phagocytosis. Infected individuals suffer from repeated infections. Once phagolysosomes are formed, the next step in phagocytosis is the generation of toxic oxygen products that are lethal to the ingested microbe. > A defect in this process can compromise phagocytosis. Chronic granulomatous disease is an inherited disorder in which the oxidative burst process is defective and phagocytic cells are unable to effectively kill the microbes they phagocytize. This disease is characterized by repeated serious infections. A third disorder of phagocyte function is myeloperoxidase deficiency. > Phagocytic cells may show an oxidative burst but be unable to produce hypochlorous acid; as a result, the phagocytes' ability to kill the microbes is compromised.

enzyme that induces programmed cell death (apoptosis)

Granzyme

Describe the potential problems that would arise if a person had an acquired inability to phagocytose pathogens. Could the person survive in a normal environment such as a college campus?

If pathogens were not phagocytized, we would not be able to present antigens so that plasma cells could make antibodies to destroy pathogens; pathogens would increase bc they wouldn't be killed through phagocytosis. The person could not survive on a college campus because of the potential pathogens that could intrude on that person's weak body.

Describe host tissue specificity for pathogens.

Infection sites for host tissues specificity is very important for infections because pathogens can only infect hosts that have the receptors that much up with the pathogen. It is the ability of cells of the adaptive immune response to interact with particular antigens. Antigens often define a particular strain of pathogen or type of foreign material. It is dependent on previous exposure to the pathogen or its products (specificity).

What are some causes of inflammation?

Inflammation is a nonspecific reaction to noxious stimuli (such as physical injury, toxins, and pathogens).

What additional type of immune cells is required for an adaptive immune response?

Mast cells and Basophils= trigger inflammation when activated Natural Killer (NK) cells= identify and destroy host cells that have become compromised and are therefore dangerous to the host (ex: cancerous)

Describe the process of phagocytosis.

Most phagocytes contain multiple membrane-bound inclusions called lysosomes, cytoplasmic vesicles containing bactericidal substances. Through the molecular mechanisms, phagocytes identify and engage pathogens on surfaces before initiating phagocytosis. Activation of phagocyte through signal transduction causes the phagocyte membrane to envelop and engulf pathogens, eventually pinching off inwardly to form a phagosome, a vacuole containing the engulfed pathogen. The phagosome then moves into the cytoplasm and fuses with a lysosome to form a phagolysosome. The toxic chemicals and enzymes within the phagolysosome kill and digest the engulfed microbial cell.

cytotoxic lymphocytes; recognize cells that do not display MHC 1 proteins, as all normal host cells should have MHC I; If a cell lacks MHC I and displays a stress protein, an NK cell will activate to destroy the target, which is likely a virally infected or cancerous host cell.

NK cells

pokes holes in the target membrane

Perforin

What major class of immune cells mediates an innate immune response?

Phagocytes= innate immune response; the primary function of a phagocyte is to engulf and destroy pathogens. A secondary function is to process the pathogen and present antigens that initiate the adaptive immune response.

Identify physical and chemical barriers to pathogens.

Physical Barriers -Skin -Flushing of urinary tract -Normal microbiota (coliforms, upper respiratory tract, vaginal canal, mouth) -Cilia in the throat help to remove particles in the nasopharynx -Mucosal membranes are coated with a thick layer of mucus -Mucus and cells lining the trachea -tight junctions between epithelial cells that line body tissues inhibit invasion and infection Chemical barriers -pH of stomach (Stomach acid inhibits bacterial growth) -lysozyme -Skin is salty and acidic, limiting bacterial growth

Describe the inflammation reaction.

Proteins called cytokines and chemokines draw white blood cells to a site of inflammation. Effective inflammatory response isolates and limits tissue damage, destroying damaged cells and pathogens. Inflammation can also inadvertently result in considerable damage to healthy tissue, particularly in key organs, such as lungs and brain tissue. Damaged cells release histamines, prostaglandins, and leukotrienes with cause vasodilation and blood goes to the injury; inflammation occurs as a reaction to a potentially tissue-damaging event.

recognize the peptide-MHC I complex on an infected cell; they secrete proteins that kill the peptide-bearing infected cell.

T-cytotoxic Cells:

Describe the circulation of a leukocyte from the blood to the lymph and back to the blood.

• The lymphatic system is separate from the blood, it drains lymph fluid from extravascular tissues o Blood is pumped through arteries and capillaries and returns from the body through veins o In capillary beds, leukocytes and solutes pass from blood into the lymphatic system o Thoracic lymph duct dumps immune cells and antibodies from the lymph into the blood o Lymph nodes contain high concentrations of lymphocytes and phagocytes

Although technically not part of the immune system, nonpathogenic normal microbiota plays a major role in preventing disease. Describe this role.

The presence of normal microbiota in the human body is critically important for resisting pathogen infection, especially on the skin and in the mucosal tissues of the gastrointestinal, respiratory, and reproductive tracts. Pathogens do not easily infect tissues on which normal microbiota are well established because the harmless microbes limit available nutrients and sites for infection by the pathogens. Although the competitive exclusion of invading pathogens by resident microbes is technically not a component of the host's immune system, the nonpathogenic normal microbiota found in or on the body play a major role in preventing disease through this principle.

What are examples of lymphoid tissue?

The primary lymphoid organs are the bone marrow and thymus. The secondary lymphoid organs are the lymph nodes, spleen, and mucosa-associated lymphoid tissue (MALT).

What types of cells are phagocytic?

The professional phagocytes include many types of white blood cells (such as neutrophils, monocytes, macrophages, mast cells, and dendritic cells).