2. All animals have innate immunity, but vertebrates alone have adaptive immunity.
3. Phagocytes and antimicrobial peptides provide invertebrates' innate immunity.
39.2 Innate Defenses Are Nonspecific and Act Early
4. Skin, mucous membranes, tears, earwax, and cilia block pathogens.
5. Phagocytes and antimicrobial substances take part in inflammation, which is an immediate reaction to injury. These protections recognize patterns of molecules that are unique to pathogens.
6. Complement proteins interact in a cascade that bursts bacterial cells.
7. Macrophages are antigen-presenting cells, engulfing, processing, and displaying foreign antigens held in place by major histocompatibility complex molecules.
10. An antibody is a Y-shaped protein composed of two heavy chains and two light chains. Each chain has a constant amino acid sequence and a variable sequence. The tips form an antigen binding site. Antibodies bind antigens and form complexes that attract other immune system components. Antibody molecules are incredibly diverse because DNA segments shuffle during early B cell development. This is the humoral immune response.
11. T cells carry out the cellular immune response. They are educated in the thymus gland to recognize self. Helper T cells activate other T cells and B cells. Cytotoxic T cells release biochemicals that bore into bacteria, kill them, and also destroy cells infected with viruses. T cells secrete cytokines, which control communication within the immune system.
16. Immune deficiency can be inherited, and some types are treatable with gene therapy.
17. Autoimmunity results when the immune system produces autoantibodies, which attack the body's tissues.
18. An allergy is an immune reaction to a harmless substance. An allergen activates IgE antibodies, which cause mast cells to release allergy mediators.
