Lymphatic System Lymphatic system: network of lymphatic vessels and organs Returns tissue fluid to the circulatory system Fights infections

Lymphatic System Lymph nodes key sites for fighting infection Packed with lymphocytes and macrophages

Immune System: Nonspecific Defense Body’s first lines of defense against infection skin, mucous membrane, enzymes, tears, acids, proteins, macrophages Nonspecific: do not distinguish one infectious microbe from another

Immune System: Nonspecific Defense Macrophages wander interstitial fluid “eat” any bacteria and virus-infected cells they encounter

Immune System: Specific Defense Specific Response: immune systems responds to foreign molecules - antigens Pathogen: foreign invader Antigen: piece of pathogen that our white blood cells recognize

Immune System: Specific Defense Two kinds of lymphocytes B cells - secrete antibodies, wander fluid T cells attack cells infected with pathogens Antigen enters the body, it activates only lymphocytes with matching receptors

Immune System: Primary and Secondary Response

Immune System: B Cells Primary vs Secondary Response B cell differentiates into: Effector cell (plasma cell) – makes antibodies Memory cell: remembers for next time

Immune System: Active vs Passive Immunity Active: when you’re cells made antibodies / longterm vaccination Passive: when given antibodies No memory cells made Short term, ex breast feeding

Immune System: T Cells T cells : when cells have been attacked Helper T cells and killer T cells Helper T cells recognize attacked cell and divide Killer T cells destroy infected cell so virus can’t multiply

Immune System: Disorders Autoimmune diseases System turns against the body’s own molecules Immunodeficiency diseases Immune system compromised Ex. AIDS virus attacks helper T Cells Physical and emotional stress may weaken the immune system