Lecture 17: Immune System Flashcards
Immune system
Primary physiological system that mediates response to harmful exogenous agents and endogenous agents- some components are active participants in metabolism
Central organs
Thymus gland and bone marre
Peripheral organs
- spleen: controls levels of blood cells (wbc, rbc, platelets)
- tonsils: stop germs entering mouth or nose
- lymph nodes: filter substances in lymph fluid
- lymph vessels: first line of defense, fluid contains lymphocytes (good), bacteria (bad)
- skin: physical barrier
- liver: designed to detect, capture, and clear bacteria, viruses, and macromolecules (carb, fat, protein)
2 functional systems
- innate: immune defenses natural/nonspecific immunity (born with)
- acquired: host defenses, referred to as adaptive/ specific immunity (develops when respond to foreign substances- antibodies)
Immune system composed of…
- blood leukocytes, or WBCs, and tissue derived from cells
Leukocytes responsible for protecting body from bacteria, virus, parasite ( formed in bone marrow and lymph tissue)- travel through blood and lymphatic tissue to ward off harmful agents
Types of leukocytes
- neutrophils: first responders
- monocytes: travel in blood to remove bacteria and travel into tissue and become macrophages
- eosinophils: attack and eliminate parasites; in mucus membranes
- basophils: release heparin, histamine, and bradykinin
- lymphocyte: part of innate immune response (NK cells) and adaptive response (T cells and B cells)
Innate immune responses
- external systems: (ex: skin and mucosa) = barriers, along with antimicrobial substances on their membranes; low pH of skin increases resistance against penetration by parasites and bacteria
- internal systems: variety of cells (principally neutrophils and monocytes) and antimicrobial substances in blood and lymph (fewer when sick)
Innate immune response: internal systems
- polymorphonuclear phagocytes ( primarily neutrophils and eosinophils): arise from stem cells in bone marrow , presence of cytoplasmic granules which contain enzymes destructive to pathogens
- mononuclear phagocytes (monocytes and macrophages): stem from cells in bone marrow, lose granules during successive differentiation
- phagocytes: eat/get ride of bacteria and other small cells
- macrophages: mobile WBCs, big phagocyte
- NK cells (natural killer): patrol and look for abnormal cells in blood and lymph
- if injured: mast cells in connective tissue detect substance and trigger allergen, release histamines
- histamines: chemical released by WBC to defend against allergen- red, heat = increase metabolic rate to repair faster; release fluids= swelling (clot blood, form scab) meanwhile lymphatic system filters fluid, clear it before back in blood stream
Acquired/ adapted immune responses
Antigens trigger immune response that learn the non-self nature of antigen- body creates antibodies against it
Acquired/ adapted immune responses: development of antibodies based on 3 components
- Recognition of specific antigenic determinant (or antigenic epitope) = portion recognized as foreign by host’s immune cells
- Proliferation of immune cells specific to antigen
- Immunologic memory = capacity of immune system to recognize and defend against antigen long after initial encounter
Acquired immune response mediated by
- antibody-mediated: (humoral) involving B cells (type of lymphocyte, WBC), production of antibodies
- cell- mediated: involving T cells (multiply and differentiate- immune response of antigen)
Immune system steps
- Macrophages engulfs pathogen, and displays pathogens antigens on its outer membrane for T-helper cells
- T helper cell binds to antigen
- B-cells specific to bacteria’s antigen are activated by T-helper cell’s proteins
- B cells engulf bacteria
- Memory cell formation: process in which B cells create memory cells which will already recognize bacteria or pathogen if attacked by same one again
Catecholamines
Important in stress response, chemical made by nerve cells- send signals to other cells (stimulate O2 consumption, other consumption- glucose and fat - thermogenesis)
myokines
Subset of cytokines, secreted by muscle cells during exercise, metabolic adaptations, tissue repair, immune function (regulation of lipid metabolism)
Immune system: exercise
- adaptive immune system is largely unaffected by exercise
- innate immune system appears to respond differentially to chronic stress of intensive exercise (NK cell activity increases, neutrophil function decreases)
- not necessarily higher incidence of infection and illness (not distinctly conclusive)
