IB BIOLOGY IMMUNE SYSTEM

• - Skin is a physical barrier which has a pH level between 3-5. This prevents some microbes from growing on the skin.
• - Sebum secreted by skin contains antimicrobial compounds and is acidic
• - Normal bacteria population helps to exclude pathogens
• - Tears, Saliva, and secretions of the mucous membranes contain lysozome
• - lysozome is a antimicrobial protein which breaks down the cell walls of many bacteria.
• - Mucous, a sticky slippery protein which traps pathogens, lines the digestive tract, urinary tract, and respiratory tracts.
• - Cilia in some locations move mucus out.

A phagocytic cell present in many tissues that functions in innate immunity by destroying microbes and in acquired immunity as a n antigen presenting cell.

body cell that produces histamine and other molecules that trigger the inflammatory response

Small proteins that direct migration of phagocytes and signal them to increase production of microbe-killing compounds.

• 1) Histamine is released by activated macrophages and mast cells at the injury site cause nearby capillaries to widen and become more permeable.
• 2) Fluid, antimicrobial proteins, and clotting elements move from the blood to the site. Clotting begins
• 3) Chemokines released by various kinds of cells attract more phagocytice cells from the blood to the injury site
• 4) Neutrophils and macrophages phagocytose pathogens and cell debris at the site, and tissue heals.

• Innate Immunity is present before any exposure to pathogens and is effective from the time of birth. Innate defenses are largely nonspecific, quickly recognizing and responding to a broad range of microbes regardless of their precise identity. Innate immunity consists of external barriers formed by the skin and mucous membranes, plus a set of internal cellular and chemical defenses that combat infectious agents that breach the external barriers.
• Key Players: macrophages, phagocytic cells

Also called adaptive immunity, develops only after to exposure to inducing agents such as microbes, abnormal body cells, toxins, or other foreign substances. Acquired defenses are highly specific and can distinguish on inducing agent from another. This recognition is achieved by lymphocytes. Lymphocytes produce 2 general immune responses: humoral response and cell mediated response

Cells derived from B lymphocytes secrete defensive proteins called antibodies that bind to microbes and mark them for elimination

cytotoxic lymphocytes directly destroy infected body cells, cancer cells, or foreign tissue.

Primary immune response is the selective proliferation and differentiation of lymphocytes that occur the first time the body is exposed to a particular antigen. The response does not peak until about 10 to 17 days after the initial exposure to the antigen. Selected B cells generate antibody secreting effector B cells (plasma cells), and selected T cells are activated to their effector forms. While these effector cells are developing, the person may become ill. Eventually, symptoms diminish as antibodies and effector T cells clear the antigen from the body

If an individual is exposed to an antigen they have been previously exposed to, a secondary immune response occurs. The response is of greater magnitude, faster (2 to 7 days), and more prolonged. Antibodies produced in a secondary response are more numerous and have a greater affinity for the antigen than those secreted in the primary immune response.

Any foreign molecule that is specifically recognized by the lymphocytes and elicits a response from them. Most are large molecules, either proteins or polysaccharides. A lymphocyte recognizes and binds to the epitope of an antigen.

A protein secreted by plasma cells (differentiated B cells) that binds to a particular antigen and marks it for elimination; also called immunoglobin. All antibody molecules have the same Y shaped structure and in their monomer form a consist of two identical heavy chains and two identical light chains joined by disulfide bridges.

• A surface protein, CD4, present on most helper T cells, binds to the II MHC molecule. This helps keep the helper T cells and the antigen presenting cell joined while activation of the helper T cell proceeds.
• A surface protein, CD8, present on most cytotoxic T cells, greatly enhances the interaction between a target cell and cytotoxic T cell. Binding of CD8 to the side of a class I MHC molecule helps keep the two cells in contact during activation of the cytotoxic T cell.

The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a close on effector cells and a clone of memory cells specific for the stimulating antigen. Clonal selection accounts for the specificity and memory of acquired immune responses.

• Like all blood cells, lymphocytes originate from pluripotent stem cells in the bone marrow. Newly formed lymphocytes are all alike, but they late develop into either T cells or B cells, depending on where they continue their maturation.
• (Lymphocytes that migrate to the thymus= T cells, Lymphocytes that remain in bone marrow= B cells)

Antibiotics interfere with cell processes in bacteria (metabolic pathways, protein formation, cell wall formation, and therefore reproduction) These are prokaryotic cell processes that are not found in eukaryotic host cells. Viruses have no cell structures, so they don't have any cell processes

Immunity conferred by natural exposure toe an infectious agent is active immunity because it depends on the action of a person's own lymphocytes and the resulting memory cells specific for the invading pathogen. Active immunity can also develop following an immunization. Immunity can also be conferred by transferring antibodies from an individual who is immune to a particular infectious agent to someone who is not. This is called passive immunity because it does not result from the action of the recipient's own B and T cells. Instead the transferred antibodies are poised to immediately help destroy any microbes for which they are specific.

• A: can receive A blood or O blood
• B: can receive B blood or O blood
• AB: can receive A, B, AB, or O blood (universal recipient)
• O: can only receive O blood (universal donor)

The Rh factor is a protein antigen on the surface of red blood cells designated Rh positive. If an Rh negative mother is exposed to blood from and Rh positive fetus, she produce anti-Rh antibodies of the IgG class. If someone is negative for the Rh factor, they can probably receive blood from an Rh person once, but any time after that memory cells will cause a reaction. A person who is positive for the Rh factor can receive blood from someone who is negative for the Rh factor without causing a reaction.

• Helper T cellsrespond to peptide antigens displayed on antigen presenting cells and in turn stimulates the activation of nearby B cells and cytotoxic T cells.
• When a helper T cell encounters and recognizes a class II MHC molecule-antigen complex on an antigen-presenting cell, the helper T cell proliferates and differentiates into a close of activated helper T cells and memory helper T cells. CD4 binds the class II MHC molecule, which helps keep the helper t cell and the antigen presenting cell joined while activation proceeds. Activated helper T cells secrete cytokines that stimulate lymphocytes which promotes cell mediates and humoral responses.

This will cause an immediate and devastating transfusion reaction. this reaction involves lysis of the transfused red blood cells, which can lead to chills, fever, shock, and kidney malfunction. Antibodies in the incompatible blood can act against the recipients own blood. The blood clots, and this ultimately causes death

• When the immune system loses tolerance for self and turns against certain molecules of the body.
• Examples: Lupus, MS, rheumatoid arthritis, diabetes

The power of antibody specificity and antigen-antibody binding has been harnessed in laboratory research, clinical diagnosis, and the treatment of disease. Some of these antibody tools are polyclonal: they are products of many different clones of B cells, each specific for a different epitope. Antibodies produced in the body following exposure to a microbial antigen are polyclonal. In contrast, other antibody tools are monoclonal: they are prepared from a single clone of B cells grown in culture. All the monoclonal antibodies produced by such a culture are identical and specific for the same epitope on an antigen.

Vaccines contain inactivated or weakened microbes, or microbe parts or toxins. When vaccines are injected, they artificially stimulate the production of memory cells through the primary immune response. A vaccinated person who encounters the actual pathogen from which the vaccine was derived will have the same quick secondary response as a person previously infected with the pathogen. Booster shots elicit a stronger secondary response and stronger immunological memory.

• Cause: of Aids is infection of helper T cells with the HIV virus, destroying the immune system
• Transmission: through blood and body fluids (semen, vaginal fluid) Heterosexual or homosexual sex,sharing or reusing needles. Almost entirely preventable disease.
• Treatment: anti-retroviral drugs are used in treatment (reverse transcriptase inhibitors and protease inhibitors)
• Social Implications: -Cases of AIDS in developing world are at a much higher rate than in industrialized nations
• -Reuse of needs in inoculation/vaccination programs
• -Women in some cultures have no control over their lives. Their husband contracts AIDS, gender inequality.
• - AIDS orphans: millions without parents because of death by HIV. Children infected as well, during childbirth or lactation
• -Pregnancy, 50% chance of infecting fetus when mother is untreated
• -Parts of South Africa, atleast 20% of the population is infected
• -Cultural Reasons: transmission between prostitutes (women) and customers (men who give it to their wives), man dies and brother i expected to marry wife, who is also infected.
• -Economic reasons: decreased government funding on research and treatment programs.