Chapter 22, part 2
The Lymphatic System and Immunity
The Thymus
Located behind sternum in anterior mediastinum
Capsule
Two lobes
Divided into lobules, each with a cortex and medulla
Cortical lymphocytes surrounded by reticular endothelial cells
Maintain blood–thymus barrier
Secretes thymic hormones: thymosins, thymopoietins, and thymulin
Figure 22.8 The Thymus
The Spleen
Largest mass of lymphoid tissue
Cellular components form pulp
Red pulp contains RBC
White pulp similar to lymphoid nodules
Spleen functions include
Removal of abnormal blood cells and other blood components
Storage of iron
Initiation of the specific immune response
Figure 22.9 The Spleen
Lymphatic system and body defenses
Nonspecific defenses
Do not distinguish one type of threat from another
7 types
Specific defenses
Protect against particular threats
Depend upon the activation of lymphocytes
SECTION 22-3 Nonspecific Defenses
Nonspecific Defenses, Physical barriers
Keep hazardous organisms outside the body
Includes hair, epithelia, secretions of integumentary and digestive systems
Figure 22.10 Nonspecific Defenses (Part 1 - Physical Barriers)
Nonspecific Defenses, Phagocytes
Remove cellular debris and respond to invasion by foreign pathogens
Monocyte-macrophage system - Fixed and free
Microphages – Neutrophils and eosinophils
Move by diapedesis
Exhibit chemotaxis
Figure 22.10 Nonspecific Defenses(Part 2 - Phagocytes)
Nonspecific Defenses, Immunological surveillance
Constant monitoring of normal tissue by NK cells
NK cells
Recognize cell surface markers on foreign cells
Destroy cells with foreign antigens
NK cell activation
Recognition of unusual surface proteins
Rotation of the Golgi toward the target cell and production of perforins
Release of perforins by exocytosis
Interaction of perforins causing cell lysis
Figure 22.10 Nonspecific Defenses(Part 3 - Immunological Surveillance)
Figure 22.11 How Natural Killer Cells Kill Cellular Targets
Nonspecific Defenses, Interferons (cytokines)
Small proteins released by virally infected cells
Trigger the production of antiviral proteins
Three major types of interferons are:
Alpha– produced by leukocytes and attract/stimulate NK cells
Beta– secreted by fibroblasts causing slow inflammation
Gamma – secreted by T cells and NK cells stimulate macrophage activity
Figure 22.10 Nonspecific Defenses(Part 4 - Interferons)
Nonspecific Defenses, Complement system
Cascade of ~11 plasma complement proteins (C)
Destroy target cell membranes
Stimulate inflammation
Attract phagocytes
Enhance phagocytosis
Complement proteins interact with on another via two pathways
Classical
Alternative
Figure 22.10 Nonspecific Defenses(Part 5 - Complement System)
Figure 22.12 Complement Activation
Nonspecific Defenses, Inflammation
Localized tissue response to injury producing
Swelling
Redness
Heat
Pain
Effects of inflammation include
Temporary repair of injury
Slowing the spread of pathogens
Mobilization of local, regional, and systemic defenses
Figure 22.10 Nonspecific Defenses(Part 6 - Inflammatory Response)
Figure 22.13 Inflammation
Nonspecific Defenses, Fever
Maintenance of a body temperature above 37.2oC (99oF)
Pyrogens reset the hypothalamic thermostat and raise body temperature
Pathogens, toxins, antigen-antibody complexes can act as pyrogens
Figure 22.10 Nonspecific Defenses(Part 7 - Fever)
