BISC 221 - The Immune System (Topic 5) - Midterm 3

What are the three strategies for defending against foreign organisms and molecules or cancer cells?

Physical and chemical surface barriers; internal cellular and chemical defenses; and specific immune responses

What is the nature of physical and chemical surface barriers?

Nonspecific; keep foreign organisms or molecules out

What is the nature of internal cellular and chemical defenses?

Nonspecific; attack any foreign organism or molecule that gets past surface barriers

What is the nature of the immune response?

Specific; destroy specific targets and remember them

What does the body’s defense system do when it works?

Defends against infection, destroys and recycles worn-out cells, and identifies/destroys abnormal cells

What happens when the body’s defense system doesn't work or overreacts?

Allergies, autoimmune diseases, and limited tissue/organ transplant success

What are the two primary types of immunity?

Innate (non-specific/inherited/rapid/no memory) and acquired (specific/adaptive/slower/memory)

What do tears do in innate immunity?

Wash away irritating substances and kill bacteria via lysozymes

What does skin provide as the first line of defense?

Physical barrier and an acidic pH to discourage organism growth

What do sweat and oil gland secretions do?

Kill many bacteria

What does saliva do?

Washes microbes from teeth and mucous membranes

What does mucus do?

Traps organisms

What do cilia do?

Sweep away trapped organisms

What does the stomach do in innate immunity?

Kills organisms with acid

What do normal bacterial inhabitants of the large intestine do?

Keep invaders in check

What does urine do in the urinary bladder?

Washes microbes from the urethra

What are phagocytes?

White blood cells that engulf pathogens

What do neutrophils do?

Circulate in the blood looking for pathogens

What do macrophages do?

Reside inside organs and tissues to engulf pathogens

What do dendritic cells do?

Stimulate the development of adaptive immunity

What do interferons do?

Slow viral reproduction, attract macrophages/natural killer cells, and prevent neighbor cell viral replication

What are interferons?

Small antimicrobial proteins secreted by virus-infected cells

What do pseudopodia do during phagocytosis?

Surround pathogens (sudo = surround)

What happens to pathogens after being surrounded by pseudopodia?

Engulfed by endocytosis, fused with lysosomes, and destroyed

What does inflammation do?

Destroys invaders and helps repair or restore damaged tissue

What causes redness during inflammation?

Mast cells releasing histamine, which dilates blood vessels

What does increased blood flow do for an injury?

Delivers defensive cells and removes dead cells and toxins

What causes heat in an inflamed area?

Increased blood flow

What does heat do for the healing process?

Speeds healing and the activities of defensive cells

What causes swelling?

Histamine making capillaries leaky, allowing fluid to seep into tissues

What does the fluid involved in swelling bring to the site?

Clotting factors, oxygen, and nutrients

What causes pain in an injured area?

Excess fluid and molecules released upon injury

What does pain do to aid healing?

Hampers movement to allow the injured area to recover

What do complement proteins do to bacteria?

Form holes in the cell wall and membrane, causing the bacterium to burst

What is the function of clot formation?

Prevents loss of blood

What is the lymphatic system?

Vessels containing lymph and various tissues/organs located throughout the body

What are lymphatic capillaries?

Microscopic, blind-ended tubules that return surplus tissue fluid to the bloodstream

Where does lymph collect into swellings?

Lymph nodes

What happens in the lymph nodes?

Adaptive immune system cells locate and process antigens (L is for locate and P is for process)

Where do B lymphocytes form and mature?

Bone marrow

Where do T lymphocytes form and mature?

Form in bone marrow and mature in the thymus gland

What are lymphocytes programmed to do?

Recognize one particular type of antigen

What causes the specificity of a lymphocyte?

Particular receptors developed on its surface

What happens when an antigen fits a lymphocyte's receptors?

Body targets that particular antigen and the lymphocyte divides into two cell lines

What are effector cells?

Short-lived cells that attack the invader

What are memory cells?

Long-lived cells that remember the invader for a quick response during future encounters

What is the first step of an adaptive immune response?

Threat (an invader enters the body)

What happens during the detection stage?

Macrophage encounters, engulfs, and digests the invader

What does a macrophage display on its surface?

Piece of the invader (antigen) with a self (MHC) marker

What happens during the alert stage?

Macrophage presents the antigen to a helper T cell and secretes an activating chemical

What is a macrophage called when it presents an antigen?

Antigen-presenting cell (APC)

What happens during the alarm stage?

Helper T cell stimulates the B cell to begin dividing

What happens during the defense stage of the B cell response?

Plasma cells secrete antibodies specific for the antigen

What happens during the continued surveillance stage?

Memory B cells remain to mount a quick response if the invader returns

What is clonal selection?

Process where a specific lymphocyte divides to produce millions of identical cells to amplify the immune response

What do cytotoxic T cells do?

Cause target cells to burst and die

What do perforins do?

Assemble into pores in the target cell membrane

What do memory cytotoxic T cells do?

Memory cytotoxic T cells remain and mount a quick response if the invader is encountered again

What defines a cell-mediated immune response?

Involvement of cytotoxic T cells

What is immunological memory?

Long-term protection against diseases via a reservoir of T and B memory cells

What is a primary immune response?

First exposure to a specific antigen where a clone of lymphocytes is formed

What is a secondary immune response?

Faster, more efficient response facilitated by memory cells during subsequent exposures

What are antigens?

Substances that elicit a response from a B or T cell

How do T or B cells bind to antigens?

Via antigen receptors specific to part of one molecule

What is an antibody (immunoglobulin)?

Soluble form of the B cell receptor secreted to mark pathogens

What are MHC molecules?

Host proteins that display antigen fragments on the cell surface

What is antigen presentation?

MHC molecules binding and transporting antigen fragments to the cell surface

What must a T cell bind to participate in the adaptive response?

Both the antigen fragment and the MHC molecule

What are plasma cells?

Effector B cells that secrete antibodies

What causes the lag phase in the primary immune response?

Cell proliferation and differentiation

What is neutralization?

Antibodies binding to viral surface proteins to prevent infection of a host cell

What is opsonization?

Antibodies binding to bacteria to trigger phagocytosis

What is the membrane attack complex?

Structure formed by complement proteins that creates pores in a foreign cell's membrane

What are the mechanisms of humoral immunity?

Agglutination, precipitation, complement activation, phagocytosis, and cell lysis

What does the humoral immune response specifically defend?

Infection of body fluids (blood and lymph)

What does the cell-mediated immune response specifically defend?

Infection of body cells

What do helper T cells do?

Activate both the humoral and cell-mediated immune responses