Lecture 15 Flashcards
First line of defense
Innate, nonspecific, includes physical (skin, mucus) and chemical barriers (low pH, digestive enzymes)
Second line of defense
Innate and mostly non-specific, WBCs inflammation, fever, complement system, interferon
Third line of defense
Specific and provides memory, T and B lymphocytes plus antibodies
Primary defenses (physical)
Skin: keratin, tough and waterproof
Mucus: traps microbes, protects body openings without skin
Cilia: moves mucus/secretions
Urine: flushes out microbes
BBB
Sneezing and coughing
Defecation and vomiting
Normal microbiota
Primary defenses (chemical)
Lysozyme in tears, saliva, sweat: enzyme hydrolyses peptidoglycan
Defensins in various cells and tissues: damage bacterial and fungal membranes
Sebum: inhibits growth
Sweat: high lactic acid and electrolytes
Hydrochloric acid in stomach
Acidic vagina
Immunology
Study of all features of the body’s second and third lines of defense
Immune system tasks
Surveillance of the body, recognition of self and foreign material, destruction of foreign entities
Major histocompatibility complex (MHC)
Protein “self tags” found on the surface of all human cells except RBCs
How MHCs are made
Exons are randomly selected from the MHC genes during development to form an individuals MHC, everyone’s MHC is different
Circulatory system immune functions
Blood carries plasma with proteins and nutrients, plasma build up causes swelling, leukocytes in blood, platelets for clotting
Lymphatic system immune functions
Provides route to return extracellular fluid to the circulatory system, drain off system for inflammatory response
Also surveillance, recognition, and protection through lymphocytes, phagocytes, and antibodies
Lymph vessels
Run parallel along blood vessels transporting lymph and collecting ECF from tissue to return to blood circulation
Lymph
Plasma like liquid that contains numerous WBCs especially lymphocytes, and infectious agents
Lymph nodes
Small bean-shaped organs stationed along the body that filter lymph fluid and house lymphocytes
Thymus
Gland above heart involved in T cell maturation
Bone marrow
Site of blood cell production
Lymphoid tissue
Patches of B and T cells found near portals of entry in the body
MALT
Mucus associated lymphoid tissue
Around areas with a lot of mucus
Lymph flow
Flows only towards the heart moved by skeletal muscle contractions of muscles surrounding lymph vessels
Basophils
Defenders against local invasion of pathogens, live in the blood, releases histamine causing inflammatory response, granulocyte
Mast cells
Mast cells line the tissue exposed to the environment, first line defenders against local invasions, release chemokines that stimulate movement of other WBCs to site of infection and histamine
Histamine
Starts inflammatory response by causing vasodilation bringing more WBCs to area
Neutrophils
Phagocytes first responders, most abundant WBC (60% +), engulf and kill bacteria
Monocytes
Circulate in blood and become macrophages when activated
Macrophage
Largest WBC, super active phagocytes, come in last and process foreign molecules plus present them to lymphocytes, overlaps with third line of defense
Eosinophils
Specialized granulocytes, active against fungal and helminth infections, use cytokines to punch holes in worms
Dendritic calls
Engulf pathogens and activate other immune cells by presenting foreign molecules to lymphocytes, taste testers
Throughout tissue that is close to the external environment
Long thin processes resemble dendrites
Overlap with third line
Lymphocytes
Third line of defense provide specific immune response and memory to foreign invaders
Two types: B and T lymphocytes
Diapedesis
Leukocytes leave the circulatory system and enter the extracellular space to check for self and non-self cells
Can be increased with chemokines released by mast cells stimulating infiltration of WBCs via a chemical gradient
Made possible by leaky capillaries and endothelial tissue of vessels
Phagocytosis by neutrophils and macrophages
- Chemotaxis and adherence of microbe to phagocyte
- Ingestion of microbe by phagocyte
- Formation of phagosome
- Fusion of phagosome and lysosome to form phagolysosome
- Digestion of ingested microbe by enzymes
- Formation of residual body containing indigestible material
- Discharge of waste material
Inflammation
Secondary defense, response to infection or chemical/physical stimuli
4 signs redness, pain, swelling, heat
Goal of inflammation
Either destroy and remove pathogen ory confine it to a specific area and stimulate tissue repair
1st response of inflammation
Vasoconstriction, prevents blood loss until clot forms, bacteria in wound signals mast cells to sound the alarm by releasing chemokines and histamine
Second response of inflammation
Histamine causes vasodilation increasing blood flow to infected area causing redness and heat given off by increased blood flow, increased vascular permeability causes leaking of fluids from blood vessels into tissue
Third response of inflammation
Swelling from increased extracellular fluid in the tissue, pressure from swelling on nerve endings causes pain, site infiltrated by neutrophils that are attracted by chemokines phagocytize sometimes forming pus
Fourth response of inflammation
Macrophages clean up debris, dead cells, leftover bacteria from infection
Fluid is reabsorbed by lymph system
Tissue either returns to normal state or scar tissue forms
Fever
Secondary defense, elevated body temperature, starts when pathogens release pyrogens that bind the hypothalamus and reset it to a higher temperature
Macrophages and other immune cells can cause never by secreting the cytokine interleukin-1, a pyrogen
Response to fever
Body tries to maintain the set temperature via changes in vasculature, metabolism, and musculature
Like shivering
Benefits of fever
Inhibits multiplication of temperature sensitive microbes, increases metabolism and stimulates immune reactions,
Dangers of fever
If temperatures get too high can damage human proteins, high or prolonged fevers especially in children need fever-suppressant drugs
Interferon (IFN)
Small protein produced by virally infected cells, bind to nearby cells and induce expression of antiviral proteins to protect nearby cells from the virus
Complement
Second line of defense 30 serum proteins that work in a cascade to destroy pathogens, proteins activated by cleavage, complement or assist in immune responses
Complement system
Complement proteins activated by self-cleavage, surround pathogen making them more appealing to macrophages, a process called opsonization, complements also form membrane attack complexes that punch holes in bacterial all membranes causing lysis, bind to mast cells signaling them to release chemokines and histamine triggering inflammatory response
Classical pathway
Antibody binding to pathogen activates complements that can lead to all 3 complement functions: opsonization, cytolysis via macrophages, and inflammation
Alternative pathway
Complement proteins bind directly to surface proteins on bacteria causing self cleavage leading to opsonization, inflammation, and cytolysis
Pathway doesn’t work if pathogen has capsule
Lectin pathway
Lectin binding to lectin receptors on pathogens activating complements leading to opsonization, inflammatory, and cytolysis
Third line of defense
Lymphocytes, B cells that mature in bone marrow, humoral immunity because found in blood and lymphatics protect bodily fluids
T cells
Mature in the thymus, engage in cell-mediated immunity, intracellular threats like viruses, pathogen has to be presented to them
