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Defenses which are specific to a particular infectious agent.

mediated by antibodies (Ab) that circulate in the blood.

• Escpecially effective in areas that are inaccessible to antibodies.
• Activiated by T-cells.
• When cells are infected with agent.

• aka. Antigenic determinates.
• areas on the molecule to which antibodies can bind.

• produced and differentiated in human bone marrow.
• produce antibodies against antigens.

• Y shaped proteins - Consists of 4 protein chains 2heavy, 2 lights.
• Variable regions 2 antigen binding sites unique for each antibody.
• have highly specific binding sites for antigens.
• 5 major constant regions which account for the 5 classes of Immunoglobulins (Ig).
• Region determine the class of antibody/Each class of IG plays a different role in Immunity.
• Where complement binds in the classical pathway.
• Recognistion site for phagocytes.

5 classes.

• IgG.
• IgA.
• IgD.
• IgM.
• IgE

• Occurs in single protein (monomer).
• prominent in blood - acccounts for 80% of all Ig in serum.
• Main antibody upon 2nd exposure.
• IgG is the only antibody to cross the placenta and give immunity to the fetus.
• activates classical complement pathway.

• Primary antibody of mucosal surfaces in Resp, Urogen, & Digest systems.
• Most abundant antibody in tissue.
• IgA may remain in your tissue or be secreted.
• Secreated IgA is a dimer.
• Colostrum, saliva, tears, sweat contain IgA.
• probable function to bind pathogens before they can attach to cells.

• Monomer structure.
• IgD antibodies are attached to the outside of B Cells.
• Acts as receptors or sensors for these cells.

• 1st antibody to appear in response to initial exposure to antigen.
• Monomer IgM found on surface of B Cells.
• IgM in blood: a pentamer: 10 antigen-binding sites.
• Responsible for reaction to blood typing.

• IgE binds to the outside of mast cells.
• When the IgE's antigen attaches, the mast cell degranulates.
• When the mast cell degranulates releases histamine.
• When the mast cell degranulates it causes inflammation and/or allergies.

• Neutralization.
• Opsonization.
• Lysis.

• Each reaction is directed toward a specific foreign antigen.
• Response to one antigen generally has no effect on other antigens.

Exposure to Infectious agent.

We get this from vaccines, also called immunizations.

We get this from our mom.

We get this from injection of antibodies from another person or animal. This can be called Gamma globulin, antitoxin, or hperimmune serum.

Genetic Factors.

• B cells originate in bone marrow. (Lymphoned stem cells differentiates into pre-B cells)
• During B cell development different variations of IgM & IgD will be attached to surface.
• During exposure, antigen binding to the IgM, or IgD on B cell will activate that cell.
• Antibody on surface of B cell encounters an antigen.
• Specific Interaction - Antigen binds to the antibody and activates the B Cell.
• Activation of the B cell.

• B Cell that was activated makes two types of B cells.
• Plasma cells whcih produce antibodies to that specific antigen.
• memory cells used for remembering the antigen in case of 2nd encounter

Memory Cells Do NOT produce antibodies.

Specific interaction, antigen binds to the antibody.

• Each activated B cell will be responsible for making only a unique antibody specific for a certain antigen.
• producing a large population of identical B cells (clone).

• B lympocites which produce and secrete massive amounts of the specifice antibody.
• Can stimulate the cell medicated response.

• long living cells for the purpose of a re-encounter with the antigen.
• creates a secondary response that is faster and stronger than the primary response.

• The first tiem the antigen or infection is encountered.
• Initial B cell clonal expansion.
• Response dominated by IgM.
• Memory cells are generated.

a measurement of antibody levels in blood (serum)

• Used to detect infection.
• Antibodies can also be isolated, purriefied and used in detection tests.

• B cell memory cells are activated.
• Memory cells differentiate into antibody producing plasma cells and produce antibody IgG instead of IgM.
• IgG appears faster and in greater quantity upon 2nd exposure.
• More memory cells are genereated.

• B lympocytes (B cells) are produced in bone morrow.
• Lympoid stem cells diffenetiates into pre-b cells

Produced in bone morrow.

Lymphoid Tissues.

T cells mature in the Thymus.

• Helper T Cells (CD4).
• Cytotoxic T Cells (CD8).
• Memory T Cells.

• Helper T Cells are activate when a macrophage and or dendritic presents the antigen to the T cell.
• these are called Antigen Presenting Cells (APC).