Immune System

What are eosinophils? What is their function? Where are they located?

Immune cells involved in defense against parasites. Account for 1-3% of leukocytes. Most are found in the digestive tract, lungs, urinary and genital epithelia, and connective tissue of skin Attach to large antibodyparasites such as Schistoma and release substances to kill target. Can also participate in allergic reactions by inflaming and damaging tissue by releasing toxic enzymes, oxidative substances, and eosinophil-erived neurotoxin

What is innate immunity?

Immunity present from birth and is nonspecific immune response. Begins within minutes to hours because of the lack of specificity. Reaction is generally inflammation

What are 5 types of antibodies?

Immunoglobulin G (IgG) Immunoglobulin A (IgA) Immunoglobulin E (IgE) Immunoglobulin M (IgM) Immunoglobulin D (IgD)

What is IgG?

Immunoglobulin G, the most common antibody found in circulation. Maternal IgGs cross the placental membrane giving infants immunity and they are also produced in secondary immune responses.

What is the hallmark reaction of innate immunity?

Inflammation

What are the two types of immunities?

Innate Acquired

Immune response pathway for a bacterial invasion

- Inflammatory response sets off several interrelated reactions -Activation of the complement system -Activation of phagocytes -Activation of the acquired immune response -Initiation of repair

Immune response pathway for a viral attack

- Similar to bacterial -Once viruses enter the host's cells cytotoxic T cell and NK cells are main defenders; however, B lymphocytes play a crucial role

What are the main functions of antibodies?

1) Act as opsonins to facilitate recognition and phagocytosis 2) Make antigens clump enhancing phagocytosis 3) Inactivate bacterial toxins 4) Activate complement 5) Activate mast cells that have IgE on their surface

What is the function of inflammation?

1) Attracts immune cells and chemical mediators 2) Produce a physical barrier to retard the spread of infection 3) Promotes tissue repair once the infection is under control Multiple molecules are involved along with cytokines

What is the immune response?

1) detects and identifies foreign substances 2) Communicate with other immune cells to mount anorganized response 3) Recruits assistance and coordinates the response among all participants 4) Destroys or suppresses the invader

What are the 5 types of leukocytes?

1) eosinophils 2) basophils 3) neutrophils 4) monocytes/macrophages 5) lymphocytes/plasma cells/dendritic cells

What are the three types of pathologies of the immune system?

1) incorrect response - autoimmune disease 2) Overactive responses - allergies 3) Lack of response - immunodeficiency diseases

What are cytokines?

A broad and loose category of small proteins (~5-20 kDa) that are important in cell signaling. They are released by cells and affect the behavior of other cells, and sometimes the releasing cell itself.

What is the secondary immune response?

A few memory cells of a clone remain waiting to respond to the next exposure of the same antigen.

What do granzymes do?

Activate an enzyme cascade to induce apoptosis.

What is IgE associated with?

Allergic response. Mast cell receptors bind with IgEs and antigen, causing the mast cells to degranulate and release chemical mediators such as histamine.

What is an allergic response?

An allergy is an inflammatory immune response to a nonpathogenic antigen which are called allergens. The immune response in allergies is called hypersensitivity to the allergen. Immediate reactions are mediated by antibodies and can occur within minutes of exposure. Delayed reactions are mediated by helper T cells and macrophages and may take several days. Allergans can be almost any exogenous molecule and can be inhaled, ingested, injected, or contact Allergies have a strong genetic component

What is the role B lymphocytes play in a viral infection?

Antibodies act as opsonins Antibody bound viruses are prevented or inhibited from entering the target cells Macrophages that ingest viruses insert fragments of antigen into MHC 2 molecules. Macrophages also secrete sytokines to promote interferon release which causes host cells to make proteins that inhibit viral replication. Other cytokines stimulate NK cells and helper T cells. Helper T cells bind to viral antigens on the macrophages which stimulates further antibody production

What are dendritic cells? What is their function?

Antigen presenting cells found in skin and all other organs. After recognizing and capturing antigens, they migrate to secondary lymphoid tissues where they present the antigen to lymphocytes. This antigen binding activates lymphocytes.

What are IgDs?

Appear on surface of B cells along with IgM but their role is unclear

What are cytotoxic T cells? How do they function?

Attack and kill cells that display MHC-1 antigen complexes by releasing a cytotoxic pore forming molecule called perforin along with granzymes that are related to the digestive enzymes trypsin and chymotrypsin. Also induce cell death by activating Fas, a death receptor protein on the target cell membrane.

What are distinguishing features of lymphocytes?

By their membrane receptors. These make each lymphocyte specific for a given ligand. All lymphocytes that are specific to the same ligand form a group known as a clone.

What are lymphocytes? What is their function? Where are they located?

Constitute 20-35% of all WBCs. Most are found in lymphoid tissue and are key cells that mediate the acquired immune response. Each of the three types function differently

What do helper T cells do?

Do not directly kill cells, but instead they secrete cytokines that influence other cells such as 1) Interferon-gamma 2) Interleukins involved with activation of antibody production, cytotoxic T cells, and 3) support of mast cells/eosinophils 4) Colony-stimulating factors Also bind to B cells and promote differentiation into plasma and memory cells. These are the target for HIV

How do clones exist before first exposure?

Each clone is represented by only a few cells called naive lymphocytes. First exposure to an antigen stimulates the clone to divide in a process called clonal expansion.

What are examples of encapsulated tissues and unencapsulated diffuse lymphoid tissues?

Encapsulated - spleen and lymph nodes Unencapsulated - tonsils and GALT

How is our immune system structured? What is the order of our defenses?

First line of defense is physical and chemical barriers from pathogens. These barriers include skin, mucus linings of GI and GU tracts, and ciliated epithelial of respiratory tract Second line of defense is innate immune response

Where is IgA located?

Found in external secretion such as saliva, tears, intestinal and bronchial mucus, and breast milk

Why are antibodies not guaranteed to be effective during a subsequent infection?

High rate of mutation in viruses causes the primary antigen to change considerably

What is the function of interferons?

Interferon-alpha and beta target host cells and promote synthesis of antiviral proteins to prevent viral replication Interferon-gamma activates macrophages and other immune cells

What are monocytes/macrophages? What is their function? Where are they located?

Less common immune cell (1-6%) Formed in bone marrow and move to their permanent position in tissues where they enlarge and differentiate into macrophages. Primary scavengers in tissue. Can ingest up to 100 bacteria as well as larger particles such as RBCs and dead neutrophils. Antigen-presenting, and thus, critical part of acquired immunity. Insert processed antigen into their surface membrane.

How do clones exist between exposures?

Lymphocytes created during clonal expansion differentiate into effector cells which carry out immediate response and memory cells.

What are neutrophils? What is their function? Where are they located?

Most abundant WBC (50-70%) Phagocytic cells that ingest and kill 5-20 bacteria during their life span of 1-2 days. Attracted to sites of damage or infection Can also release a variety of cytokines, fever-causing pyrogens, and chemical mediators of inflammatory response

What are natural killer lymphocytes?

Participate in innate response against viral infections by inducing viral infected cells to undergo apoptosis. Specific response required to completely eliminated. Release interferons to fuk up replication

Describe leukocytes

Primary cells of immune system that circulate in the blood and leave the capillaries to function outside of the vessels. Life span - hours to months

What is IgM associated with?

Primary immune responses and with antibodies that react to blood roup antigens. Activate complement

What are phagocytes? What is their function?

Primary phagocytic cells of immune system are macrophages and neutrophils. Suppress invaders by digesting them and releasing cytokines to attract additional immune cells. Once a pathogen has been ingested it ends up in aa vesicle called a phagosome where it is destroyed by enzymes and oxidizing agents.

What is the function of the immune system?

Protects the body from disease causing invaders (pathogens). Removes dead or damaged cells Recognizes and removes abnormal cells

What are basophils? What is their function? Where are they located?

Rare in circulation and similar to mast cells. Release mediators that contribute to inflammation such as histamine, heparin, cytokines and other chemicals. Found in connective tissue of skins, lungs, and GI tract where they can intercept pathogens that are inhaled, ingested, or enter through breaks in the epidermis

What are secondary lymphoid issues? What are the divisions?

Sites where mature immune cells interact with pathogens and initiate a response. Divided into encapsulated tissues and unencapsulated diffuse lymphoid tissues.

What is the primary immune response of a clone of B lymphocytes?

Some of the cells in a clone of B lymphocytes differentiate into plasma cells that do not have antibody proteins in their membranes. These cells synthesize and secrete additional antibodies at a rate of ~2000/sec

What is acquired immunity?

Specific immune response. May take several days to respond to first exposure; however, with repeated exposures the immune response is more rapid. Can be divided into cell-mediated immunity and humoral immunity

What do T lymphocytes do? How? Where do they develop?

T lymphocyes defend the body against intracellular pathogens binding to cells that display foreign fragments as part of a major histocompatibility complex (MHC) on their surface. T cells develop in the thymus gland and mature T cells bind to MHC antigen presenting cells with the help of T cell receptors.

What are the two primary lymphoid tissues? What is common to the two?

Thymus gland bone marrow Both sites are where cells involved in immune sites form and mature

What is an antibody molecule composed of?

Two identical light chains and two identical heavy chains, linked by disulfide bonds

How does passive immunity occur?

We acquire antibodies made by another animal e.g. from mother to fetus across he placenta. Another example is getting injections containing antibodies

How are phagocytosis and cytoxic cells initiated?

When the Fc region of an antigen bound antibody is bound to the phagocyte org cytoxic cell

What are leukocytes?

White blood cells