BIOS 2150 Microbiology -The Adaptive (Specific) Immune System

The Adaptive (Specific) Immune System (Chapter 18) • Adaptive immunity: defenses that target a specific pathogen o Learned- the body has to adapt to this o Some pathogens change their shape so that adaptive immunity misses them • Acquired through infection or vaccination o Immune response is always stronger through infection • Primary response: first time the immune system combats a particular foreign substance • Secondary response: later interactions with the same foreign substance; faster and more effective due to “memory” Dual Nature of the Adaptive Immune System 1. Humoral immunity . Produces antibodies that combat foreign molecules known as antigens . Antibodies are made by a type of B cell lymphocyte (white blood cell) . Named for the bursa of Fabricius in birds . Humoral immunity fights invaders outside cells . Bacteria and toxins for example . Done in lymph (done in blood) . Antibodies are secreted all over the body . Lymph, blood, saliva, milk, line the digestive system 2. Cellular Immunity (cell-mediated immunity) . Does not make antibodies . Produces T cell lymphocytes (white blood cells) . Mature in the thymus . Attack antigen inside of cells . Antibodies cannot get inside of cells . Release chemicals that kill infected cells Cytokines: Chemical Messengers of Immune Cells • Cytokines are chemical messengers produced in response to a stimulus o Examples:  Interleukins: cytokines between leukocytes  Chemokines: induce migration of leukocytes  Interferons (IFNs): interfere with viral infections of host cells  Tumor necrosis factor (TNF): involved in the inflammation of autoimmune diseases  Hematopoietic cytokines: control stem cells that develop into red and white blood cells  Overproduction of cytokines lead to a cytokine storm • Function of cytokines? Chemicals from white blood cells that activate the immune system Antigens • Antigens: substances that cause the production of antibodies • Usually components of invading microbes or foreign substances • Haptens: antigens too small to provoke immune responses; attach to carrier molecules to become antigenic (many allergens are considered haptens) Antibodies • ANTIBODIES ARE MADE OF PROTEIN • Globular proteins called immunoglobulins (Ig) • Made by B cells Generating Antibody-Producing Cells: • Inactive B cells contain surface antibody (membrane-bound antibody) that bind to antigen Clonal Selection of Antibody-Producing Cells • Clonal selection differentiates activated B cells into: o Antibody-producing plasma cells  Plasma Cell • Secretes antibody • Short life span o Hours maybe days o Memory cells  Produce lots of antibodies in a short time  Long life span • Can be months, years, or whole life depending on the particular memory cell  Memory cell is all about your secondary exposure