Chapter 17: Adaptive Immunity Flashcards
Adaptive Immunity is the body’s ability to react specifically to a microbial infection
- the body’s response to the first contact with a particular antigen is called the primary response…specific cells are activated to destroy the antigen (??? is this talking about innate or adaptive)
- memory cells respond to subsequent contact with the same antigen
Dual nature of the Adaptive Immune System:
- humoral immunity involves antibodies, which are found in serum and lymph and produced by B cells
- lymphocytes that mature in red bone marrow become B cells
- cellular immunity invovles T cells
- lymphocytes that migrate through the thymus become T cells
- T cell receptors recognize antigens presented on MHC
- cellular immunity responds to intracellular antigens; humoral immunity responds to antigens in body fluids
Cytokines: Chemical Messengers of Immune Cells
- cells of the immune system communicate with each other by means of chemicals called cytokines
- interleukins (IL) are cytokines that serve as communicators between leukocytes
- chemokines cause leukocytes to migrate to an infection
- interferon-y stimulates the immune response; other INFs protect cells against viruses
- tumor necrosis factor promotes the inflammatory reaction
- hematopoeitc cytokines promote development of WBCs
- overproduction of cytokines leads to a cytokine storm, which results in tissue damage
Antigens and Antibodies: Antigens
- an antigen (or immunogen) is a chemical substance that causes the body to produce specific antibodies
- as a rule, antigens are proteins or large polysacccharides; antibodies are formed against specific regions on antigens called epitotes (or antigenic determinants)
- a hapten is a low-molecular-mass substance that cannot cause the formation of antibodies unless combined with a carrier molecule; haptens react with their antibodies independently of the carrier molecule [Haptens are small molecules that elicit an immune response only when attached to a large carrier such as a protein; the carrier may be one that also does not elicit an immune response by itself.]
Antigens and Antibodies: Humoral Immunity Antibodies
-an antibody, or immunoglobulin, is a protein produced by B cells in response to an antigen and is capable of combining specifically with that antigen
Antigens and Antibodies: Humoral Immunity Antibodies
- typical monomers consist of four polypeptide chains: two heavy chains and two light chains. They have two antigen-binding sites
- –within each chain is a variable (V) region that binds the epitope and a constant (C) region that distinguishes the different classes of antibodies
Antigens and Antibodies: Humoral Immunity Antibodies
- an antibody monomer is a Y-shaped or T-shaped: the V regions form the tips, and the C regions form the base and Fc (stem) region
- the Fc region can attach to a host cell or to complement
Antigens and Antibodies: Humoral Immunity Antibodies
The IgG antibody is the most prevalent in serum; they provide naturally acquired passive immunity, neutralize bacterial toxins, participate in complement fixation, and enhance phagocytosis
Antigens and Antibodies: Humoral Immunity Antibodies
IgM antibodies consist of five monomers help by a joining chain; they are involved in aggulation and complement fixation
Humoral Immunity Response Process:
- B cells have antibodies on their surfaces, which recognize specific epitopes
- For T-independent antigens, a clone of B cells is selected
- For T-dependent antigens: the B cell’s immunoglobulins combine with an antigen, and the antigen fragments, combined with MHC class II, activate TH cells. The TH cells activate a B cell
Humoral Immunity Response Process: Activation and Clonal Expansion of Antibody-Producing Cells
- activated B cells differentiate into plasma cells and memory cells
- plasma cells produce IgM antibodies and then produce other classes, usually IgG
- B cells that recognize self are eliminated by clonal deletion
- Immunoglobulin genes in B cells recombine so that mature B cells each have different genes for the V region of their antibodies
Humoral Immunity Response Process: Results of the Antigen-Antibody Interaction
- an antigen-antibody complex forms when an antibody binds to its specific epitopes on an antigen
- aggulation results when an antibody combines with epitotes on two different cells
- opsonization enhances phagocytosis of the antigen
- antibodies that attach to microbes or toxins and prevent them gaining access to the host or performing their action cause neutralization
- complement activation results in cell lysis
Humoral Immunity Response Process: Cellular Immunity Response Process
-T-cells mature in the thymus gland…thymuc selection removes T cells that don’t recognize MHC molecyles of the host and T cells that will attach host cells presenting self proteins in MHC
- helper T cells recognize antigens processed by antigen-presenting cells and presented with MHC II
- cytotoxic T cells recognize antigens processed by all host cells and presented with MHC Class I
Humoral Immunity Response Process: Cellular Immunity Response Process
-T-cells mature in the thymus gland…thymuc selection removes T cells that don’t recognize MHC molecyles of the host and T cells that will attach host cells presenting self proteins in MHC
- helper T cells recognize antigens processed by antigen-presenting cells and presented with MHC II
- cytotoxic T cells recognize antigens processed by all host cells and presented with MHC Class I
Humoral Immunity Response Process: Antigen-Presenting Cells (APCs)
- APCs include B cells, dendritic cells, and macrophages
- dendritic cells are the primary APCs
- activated macrophages are effective phagocytes and APCs
- APCs carry antigens to lymphoid tissues where T cells that recognize the agent are located
