Adaptive Immunity

—Works together with inflammation. Recognizes foreign or “nonself” substances. Provides Long term protection. Slower than innate but more specific. has memory

–Pathogens– Noninfectious environmental agents –Drugs –Vaccines– Transfusions Transplants

—End-products of adaptive immunity Lymphocytes:

End-products of adaptive immunity: Antibodies

◦Each individual T or B cell specifically recognizes only one particular antigen. ◦Sum of the population of lymphocyte specificities may represent millions of foreign antigens.

Primary Lymphoid organs (2)

Occurs in primary lymphoid organs. Involves the maturing of B and T cells. Migrates to secondary lymphoid organs.

Antigen is processed and presented to immune cells by antigen-presenting cells (APCs). Cellular interaction of T-helper cells (Th) and APCs. –Results in the differentiation of B cells into active antibody-producing cells and T cells

B cells turn into Active antibody producing cells also called

T cells turn into

B cells and circulating antibodies are the primary cells. Causes direct inactivation of a microorganism or the activation of inflammatory mediators. Primarily protects against bacteria and viruses.

◦Differentiates T cells. Primarily protects against viruses and cancer. Kills targets directly or stimulates activity of other leukocytes.

Humoral and cellular immunity work together to provide ____ and ____. Respond more rapidly and efficiently on subsequent exposure to the same _____

Antibodies or T cells are produced after either a natural exposure to an antigen or after immunization. Is long lived.

active or passive immunity

Preformed antibodies or T lymphocytes are transferred from a donor to a recipient. Occurs naturally or artificially. Is temporary or short lived.

active or passive immunity

—required for a successful immune response.— Are complicated processes and involve a highly effective interaction of cells.

Originally was used to describe proteins found on the surface of lymphocytes. Currently used as a labeling system used to identify a family of proteins on many cells.

—Is a molecule that can react with antibodies or receptors on B and T cells.— Is mostly protein but can be other molecules as well.

—An antigen that can trigger an immune response

Antigen’s binding site: antigenic determinant

Antibody or lymphocyte’s binding site: Antigen-binding site

Degree to which antigen has _____ capability is degree of foreignness to host (most important), size, chemical complexity, amount

Small–molecular-weight antigens are called_____. –Cannot trigger the immune response themselves but can when bound to a carrier protein.

–The greater the diversity, the more the immunogenicity. dealing with Antigen

––antigens in High or low extremes can cause tolerance.

—We recognize ourselves as not foreign.

Lymphocytes with receptors against self-antigens are eliminated.

Prevents recognition by lymphocytes and antibodies.

antibodies are also called

antibodies are produced by

Antibodies have several classes –characterized by antigenic, structural, and functional differences. (5)

Is the most abundant class (80% to 85%). Is transported across the placenta. Accounts for most of the protective activity against infections. most prevalent. Most protective activity against infection. Crosses placenta. most prevalent

in body secretions are dimers anchored by the J-chain and “secretory” piece.– Secretory piece may function to protect ___ against enzyme degradation.

type of IgA that is predominantly in the blood

Type of IgA predominantly in normal body secretions.

Is the largest of the immunoglobulins. Pentamer is stabilized by a J-chain. Is the first antibody produced during the primary response to an antigen. Is synthesized during fetal life.

Information limited. Concentration is low in the blood. Is located primarily on the surface of developing B lymphocytes. Functions as one type of B-cell antigen receptor.

Is the least concentrated of the immunoglobulin classes in the circulation. Acts as a mediator of many common allergic responses. Defends against parasites.—

Antibody molecular structure: Acts as recognition sites (receptors) for antigenic determinants; binds antigen; has two identical fragments.

Antibody molecular structure: Is responsible for biologic function.– Activates complement and opsonization.

Antibody molecular structure: Two light chains and two heavy chains are held together with disulfide bonds.– Heavy chain determines the type of antibody.

—Amino acid sequences of the variable regions of the heavy and light chains—. Framework regions that control antibody folding

◦Noncovalent chemical interactions

IgG, IgD, circulating IgA and IgE—2 Secretory IgA—4 IgM—theoretically 10, likely 5

number of binding sites

—Is located on the surface of B cells.

–Membrane-associated IgM and IgD. –Responsible for recognition and binding

–Ig-alpha and Ig-beta heterodimers–. Responsible for sending message to mature and to make antibodies

Antibody-like transmembrane protein (TCR)–. Are responsible for recognition and binding. Accessory proteins for intracellular signaling. –Are referred to as CD3. –Are responsible for sending message to activate and differentiate T cells.

—Are needed for an effective immune response.— Antigen is processed within cells.— Are expressed on the cell surface in a specific manner.— Some antigens need special APCs; others can be processed by most any type of cell.

◦Glycoproteins on the surface of all human cells (except red blood cells [RBCs])◦Human leukocyte antigens (HLA) alleles: Inherited in a co-dominant fashion to enable both maternal and paternal antigens to be expressed ◦Are also called HLAs◦MHC class I genes: A, B, and C◦MHC class II genes: DR, DP, and DQ◦MHC class III genes: Other genes that control the quality and quantity of an immune response

—Is a specific combination of alleles at the six major HLA loci on one chromosome (A, B, C, DR, DQ, and DP).

—Cells in transplanted tissue from one individual have a different set of MHC surface antigens than those of the recipient. —The recipient can mount an immune response against foreign MHC molecules. —The more similar two individuals are in HLA tissue type, the more likely for a successful transplant.

—Antigen-presenting molecules. —Found on APCs and thymus cells. —Present lipid antigens◦(Mycobacterium tuberculosis and Mycobacterium leprae)

—Antigen-independent interactions between cells. —Resulting in intracellular signaling events that are independent of the TCR or BCR complexes. —Necessary complement to antigen-specific signaling. —Needed for effective immune response.

—Low–molecular-weight proteins, or glycoproteins, function as chemical signals between cells. Are secreted by APCs and lymphocytes.

Cytokines increase the production of

Influences given cell that ultimately determines that cell's response. lymphocytes proliferate and differentiate in result.

—All necessary receptor specificities are produced.— Takes place in the primary (central) lymphoid organs. Thymus for T cells, bone marrow for B cells—. Results in immature but immunocompetent T and B cells.— Migrates to secondary lymphoid organs to wait for antigens. Primarily occurs in the fetus

—Usually beings at birth and proceeds throughout life. —Is a process by which antigen selects lymphocytes with complementary TCRs or BCRs.

initiated by antigen. Expands the population and causes differentiation into antibody-secreting plasma cells or mature T cells or both.

Deoxyribonucleic acid (DNA) is cut and spliced. Each cell is unique and able to react with different antigens.

central lymphoid organ of T-cell development.

—T cells move from the thymic cortex to the medulla.— Changes include the development of the TCRs and the expression of surface molecules. —T cells are released into the blood and take up residence in the secondary lymph organs to await antigens.

—Produce changes in characteristic surface markers (TCR, CD4, CD8)

CD2 is a marker for

recognize antigens presented by MHC class II molecules and develop into Th cell

recognize antigens presented by MHC class I molecules and become mediators of cell-mediated immunity and directly kill other cells (T-cytotoxic [Tc] cells).

Autoreactive T cells in the thymus are deleted

◦A TCR strongly reacts with MHC class I or class II; the T cell will undergo apoptosis.

◦Developing T cell’s TCR binds strongly with a self-antigen causing T cell to be deleted.

◦Surface CD4 molecules bind to MHC class II molecules and become CD4 single–positive; surface CD8 reacts with MHC class I molecules and become CD8 single–positive. –60% of immunocompetent T cells being CD4+ and 40% being CD8+.

—Occurs in the bone marrow.— Stem cell matures. ◦CD45R and the interleukin (IL)–7 receptor–IL-7: Is produced by stromal cells; is critical in driving the further differentiation and proliferation of the B cell.

—Production of BCRs. Heavy and light chains. V, D, and J genes

Complement receptor

◦Adhesion molecule required for later interactions with Th cells

◦Large number of autoreactive B cells are eliminated if exposed to self-antigen—over

—Include the spleen, lymph nodes, adenoids, tonsils, Peyer patches (intestines), and appendix.

—Lymphocytes bind to the endothelium through adhesion molecules.

Antigens require processing and presentation by

–Present antigen to Th cells that facilitate humoral immune response

Present antigen to memory Th cells to initiate a rapid response to antigens

–Process antigen from a site of inflammation to T-cell–rich areas of lymph nodes

◦Antigen processing: Is the process by which exogenous and endogenous antigens are linked with the appropriate ___ molecules.

◦Generally present endogenous (inside cells) antigens.

◦Prefer exogenous (outside cells) antigens.

—Th cells help the antigen-driven maturation of B and T cells.—Facilitate and magnify interaction between APCs and immunocompetent lymphocytes.