Chapter 15

1. bind antigens 2. "red flag"

1. Antibodies protect the host by both direct and indirect mechanisms. The direct effect is due to their ability to -----. Simply by doing so , they can coat an antigen, thereby preventing it from attaching to a host cell. 2. The indirect protective effect is due to the ----region tagging the antigen for elimination

B cells,

--- are responsible for humoral immunity. In humans, however, they develop in the bone marrow

TH2

----- activate eosinophils and B cells to produce IgE

Primary lymphoid organs

----- include bone, thymus Once mature, lymphocytes gather in secondary lymphoid organs and wait to encounter antigen

The lymphatic system lymphocyte

----- is a collection of tissues and organs that bring the population of B cells and T cells into contact with antigens This is important because each ------recognizes only one or a few different antigens.

Antibody titer

----- is the amount of Ab in serum

humoral immunity

-----, works to eliminate extracellular antigens—for example, bacteria, toxins, or viruses in the bloodstream or in tissue fluids.

Neutralization.

------ Toxins and viruses must bind specific molecules on a cell surface before they can damage that cell. A toxin or virus coated with antibodies cannot attach to cells and is said to be neutralized.

Effector lymphocytes

------ are descendants of activated lymphocytes: plasma cells, TC cells, TH cells

Naive lymphocytes

------- have receptors; have not yet encountered appropriate antigen

Secondary (memory or anamnestic) response

-------occurs after second exposure with Antigen.

Memory lymphocytes

------are long-lived descendants of activated lymphocytes; responsible for rapid secondary response if antigen encountered again

TH

------cell produces cytokines that activate the B cell

Th

------cells help orchestrate the various responses of humoral and cell-mediated immunity. They activate B cells and macrophages, and produce cytokines that direct and support T cells.

Natural Killer

------cells induce apoptosis in "self" cells and recognize host cells with foreign proteins in membrane bound by antibodies

TH1

------produces IFN-gwhich activates cells related to cell-mediated immunity, macrophages, and Abs

Antibodies, Fab regions Fc - can be crystallized

-----also called immunoglobulins, are Y-shaped proteins that have two genera parts—the arms and the stem The two identical arms, called the-----, bind antigen. The stem is the ----region

Dendritic cells

-----are responsible for T-cell activation; recall that these cells are a part of innate immunity. Once activated, a T cell proliferates and then differentiates to form effector T cells, armed to perform distinct protective roles.

Tc Virally

-----cells respond to intracellular antigens (antigens within a host cell). When they find such an antigen, they induce the "self cell that harbors it to undergo apoptosis. ------infected cells provide a good example of the effectiveness of this strategy. By inducing these cells to undergo apoptosis, the immune system destroys cells that would otherwise produce more viral particles. Sacrifícing the cells also releases unassembled viral components, provoking a humoral response as well

Clonal deletion

-----eliminates harmful B cells

Immature lymphocytes

-----lack fully developed antigen-specific receptors

T-independent antigens

----Stimulate the B cell to make Abs but no memory cells

T-independent

----antigens can activate B cells without Th cell help. They include lipopolysaccharide (LPS) and molecules with repeating subunits, such as some carbohydrates.

NK

----cells bind, deliver perforin- and protease-containing granules to cell, initiating apoptosis Also recognize host cells lacking MHC class I Some viruses interfere with antigen presentation

Activated lymphocytes

----have bound antigen and received confirmation, are able to proliferate

Primary response

----occurs after initial contact with Ag

cell-mediated Immunity (CMI), or cellular immunity,

---deals with antigens residing within a host cell, such as a virus infecting a cell.

Y-shaped proteins called antibodies

In response to extracellular antigens, B cells may be triggered to proliferate and then differentiate into plasma cells, which function as factories that produce ------. These molecules bind to antigens, providing protection.

igE

Monomer 0.002% of serum Abs On mast cells, on basophils, and in blood "Allergic reactions"; lysis of parasitic worms Half-life = 2 days is barely detectable in blood, because most is tightly bound via the Fc region to basophils and mast cells, rather than being free in the circulation.

igD

Monomer 0.2% of serum Abs In blood, in lymph, and on B cells ( It is involved with the development and maturation of the antibody response) On B cells, initiate immune response Half-life = 3 days

igG

Monomer 80% of serum Abs Fix complement In blood, lymph, and intestine Cross placenta ---An important characteristic of it is that it is transported across the placenta into the fetus's bloodstream, so it protects the developing fetus against infections. Enhance phagocytosis; neutralize toxins and viruses; protects fetus and newborn Half-life = 23 days, provides the longest-term protection of any antibody class

T-dependent

Most antigens are -----antigens, meaning that the responding B cell requires assistance from a Th cell in order to become activated. have a protein component.

defend the body, neutralize toxins and viruses that have not yet invaded cells.

Once antibodies bind to antigen they form large complexes which ------ and -----

igM

Pentamer 5-10% of serum Abs Fix complement In blood, in lymph, and on B cells Agglutinates microbes; first Ab produced in response to infection Half-life = 5 days

opsonization.

Phagocytic cells have receptors for the Fc region of IgG molecules, making it easier for the phagocyte to engulf antibody-coated antigens the complement protein C3b opsonizes antigens; IgG molecules have a similar effect.

Secondary Lymphoid Organs

Sites where lymphocytes gather to contact antigens Lymph nodes, spleen, tonsils, adenoids, appendix

thymus Thymic selection T-cell receptors (TCRs) antigen-presenting cells (APCs) age. CD, membrane proteins needed for adhesions of molecules.

T Cells and Cellular Immunity T cells mature in the ---- ------eliminates many immature T cells T cells respond to Ag by ----- T cells require ------- Ability to make T cells decreases with---- Different types of T cells: TH cells, TC cells and Treg. They are classified by -----

Naturalization, Opsonization Complement system activation, immobilization and prevention of adherence.

The protective outcomes of antibody-antigen binding (figure 15.8) depend partly on the antibody class, and include:----- , ------ , ------, and -----

The Lymphatics or lymphatic vessels

These vessels carry lymph, a fluid that forms as a result of the body's circulatory system Contains white blood cells and antigens from tissues

Natural Killer cells

have Antibody-dependent cellular cytotoxicity (ADCC) these cells have FC receptors for IgG molecules

memory B cells,

A high degree of specificity is involved in the binding, so many different antibody molecules are needed to bind to the wide array of antigens encountered throughout life. Some of the B cells form ----- long-lived cells that respond more quickly if the antigen is encountered again.

Regulatory T cells

A third T-cell subset,-------are similar to the other T cells in that they have a TCR, but their role is entirely different. Instead of fostering a response, they help prevent the immune system from mounting a response against "self molecules; failure to do this results in autoimmune diseases

1. macrophage or dendritic 2. MHC proteins 3. activated. 4. T Hcells a 5. TC cells

Activation of T cells 1. A ------or --------cell phagocytize the pathogen which is then degraded. 2. They insert the pathogen pieces on----- which are located on the host cell membrane. 3. When the macrophage presents the processed antigen to the T cell that has the appropriate antigen receptor, it gets------- 4. -----are activated by Ag present on MHC class II 5. ---are activated by Ag present on MHC class I

antigenic determinants or epitopes

Antibodies usually recognize and interact only at specific parts called as ------ than the whole antigen. These are stretches of 10 or so amino acids, whereas others are three-dimensional shapes such as a region that sticks out in a mol¬ecule

Constant Regions:

Antibody Structure ----- Stem of monomer and lower parts of Y arms. (This Region includes the entire Fc region, as well as part of the two Fab regions The consistent nature of this region allows other components of the immune system to recognize the otherwise diverse antibody molecules. There are five general typesand these correspond to the major classes of immunoglobulin (Ig) molecules— IgM, IgG, IgA, IgD, and IgE. )

Fc region:

Antibody Structure ----- includes Stem of monomer only. Important because they can bind to complement or cells.

Monomer

Antibody Structure -----: A flexible Y-shaped molecule with four protein chains: 2 identical light chains - ( a lower-molecular-weight polypeptide chain) 2 identical heavy chains -( high-molecular- weight polypeptide chain),

Variable Regions

Antibody Structure -----: Two sections at the end of Y's arms. Contain the antigen binding sites (Fab). Identical on the same antibody, but vary from one antibody to another.

specific antigen molecules; amino acid sequence "red flag," tagging antigen bound by antibodies and enlisting other immune system components to eliminate the molecule.

Antibody molecules have two functional regions—the two identical arms and the stem of the molecule. The arms bind----- the ----- of the end of the arms varies among antibodies, providing the basis for their specificity. The stem functions as a ------

Complement system activation.

Antigen-antibody complexes (commonly called immune complexes) can trigger the classical pathway of When multiple molecules of certain antibody classes are bound to a cell surface, a specific complement system protein attaches to their Fc regions, initiating the cascade. Recall that activation of the complement system results in production of the opsonin C3b, initiation of an inflammatory response, and formation of membrane attack complexes.

membrane-bound receptors BCR TCR

B cells and T cells have ------- whose Function to recognize specific antigens ---- is specific antibody the B cell is programmed to make ----does not recognize free antigen; must be presented by body's own cells

Antibody-producing plasma cells Memory cells

B cells differentiate into ----- and -----

MHC class II molecules

BCell activation When a B cell's antigen receptor (B-cell receptor) binds to a T-dependent antigen, the B cell takes the antigen in by endocytosis, enclosing it within an endosome. There, the antigen is degraded into peptide fragments that are then delivered to protein structures called --------. These move to the B-cell surface, where they "present" pieces of the antigen for inspection by T^ cells—a process called antigen presentation

Immobilization and prevention of adherence.

Binding of antibodies to flagella interferes with a microbe's ability to move; binding to pili prevents it from attaching to surfaces. These capabilities are often necessary for a pathogen to infect a host, so antibodies that bind to flagella or pili prevent infection.

T Regulatory Cells

CD4 and CD25 on surface Suppress T cells against self

1. TCRs , MHC II 3. cytokines TH1 TH2 Memory cells

CD4+ or TH cells 1. ---- recognize Ags and -----on APC 2. TLRs are a costimulatory signal on APC and TH 3. TH cells produce ----- and differentiate into ----, ------and -------

1. self carrying endogenous antigens 2. cytotoxic T lymphocytes (CTLs) 3. perforin and granzymes

CD8+ or TC cells 1. Target cells are ------ 2. Activated into------ CTLs recognize Ag + MHC I Induce apoptosis in target cell 3. CTL releases ------ and ---------

Antigen-Presenting Cells

Digest antigen Ag fragments on their surface with MHC Include B cells, Dendritic cells and Activated macrophages

igA

Dimer 10-15% of serum Abs In fact, IgA is the most abundant immunoglobulin class produced. In secretions- The secreted form is important in mucosal immunity and is found on the mucous mem¬branes Mucosal protection Half-life = 6 days

Antigen

Host should perceive as foreign.