Lecture 12: Innate Immunity Flashcards
What is susceptibility?
Likelihood of acquiring/lack of resistance to a disease
What is resistance?
Ability to ward off disease
What is innate resistance?
Resistance due to physiological processes of humans that are incompatible with those of the pathogen
Chemical receptors for pathogens are not present on human cells
Temperature and pH may be incompatible with those necessary for the pathogens survival
What is acquired resistance?
Resistance to an infectious agent due to prior contact with that agent
What is nonspecific resistance?
Innate, defense against any pathogens
What is specific resistance?
Acquired, defense against specific pathogens
What is the first line of defense?
A surface protection composed of anatomical and physiological barriers that keep microbes/ pathogens from entering the body
-physical barriers (intact skin)
-microbiota barrier (normal microbiota (flora))
-chemical barriers (mucous membranes and their secretions)
Discuss the mechanical factors of intact skin
Epidermis
-outer layer composed of multiple layers of tightly packed cells
-few pathogens can penetrate these layers
-shedding of dead skin cells removes attached microorganisms
Dermis
-contains protein fibers called collagen and keratin
-give skin strength and pliability to resist abrasions that could introduce microorganisms
Discuss the mechanical factor - mucous membrane
Line all body cavities open to the outside environment (oral cavity, digestive system,.)
Two distinct layers:
(1) Epithelium: thin, outer covering of the mucous membranes
-tightly packed
-shed continually
-used for absorption
-contain goblet cells which produce sticky mucus that traps bacteria and pathogens
(2) Depper connective layer that supports the epithelium
Discuss the mechanical factor - ciliary escalator
Microbes trapped in mucus are transported away from the lungs
Discuss the mechanical factor - lacrimal apparatus
Tears: washes eyes
Discuss other mechanical factors like saliva, urine, vaginal secretions
Saliva: washes microbes off
Urine: flows out
Vaginal secretions: flow out
Discuss chemical factor, perspiration
Perspiration secreted by sweat glands
salt- inhibits growth of pathogens
Discuss chemical factor, low pH
skin (3-5) and gastric juice (1.2-3.0)
Discuss chemical factor, lysozyme
Lysozyme destroy cell wall bacteria
in tear, saliva, nasal secretions, tissue fluids
Discuss chemical factor, sebum
Sebum secreted by sebaceous (oil) glands (fatty acid)
Helps keep skin pliable
Lowers the pH of the skin
Fungistatic
Discuss chemical factor, transferrins
Transferrins in blood find iron, making iron unavailable for bacterial growth
Discuss microbial antagonism/ competitive exclusion when normal microbiota compete with pathogens
normal microbiota compete with pathogens:
Secrete antimicrobial substances that limit pathogen growth
Consumption of nutrients makes them unavailable to pathogens
Create an environment unfavorable for other microorganisms by changing pH
What is the immune system?
A healthy immune system is responsible for:
-surveillance of the body
-recognition of foreign materials
-destruction of entities deemed to be foreign
Discuss neutrophils and eosinophils?
Can phagocytize pathogens
Are capable of diapedesis
What are the body compartments with immune functions?
The reticuloendothelial system (RES)
The extracellular fluid (ECF) surrounding tissue cells
The blood stream
The lymphatic system
What is the composition of whole blood?
Composed of cells and portions of cells within a fluid called plasma
Plasma is mostly water containing electrolytes, dissolved gases, nutrients, and proteins
- after clotting, remaining fluid is called serum (therapy and testing)
- plasmas proteins include complement proteins and antibodies
-the cells and cell fragments in plasma are called formed elements
Buffy coat: white layer, 1%, WBCs
What are granulocytes and their three types?
Contain large granules that stain different colors based on the dye used
3 types:
Basophils
Eosinophils
Neutrophils
What are the three types of formed elements?
Erythrocytes: carry oxygen and carbon dioxide in the blood
Platelets: involved in blood clotting
Leukocytes: involved in defending the body against invaders
2 groups: Granulocytes and Agranulocytes
What is hematopoiesis?
Production of blood cells
What are neutrophils?
Stain lilac with a mixture of acidic and basic dyes
What are basophils?
Stain blue with the basic dye methylene blue
What are eosinophils?
Stain red/orange with the acidic dye eosin
What is the reticuloendothelial system?
Tissues of the body are permeated by a support network of connective tissue fibers that interconnect nearly cells to create a massive network surrounding all organs
What are agranulocytes?
Cytoplasm appears uniform under a light microscope
2 types:
lymphocytes
monocytes
What are lymphocytes?
Most involved in specific immunity
What are monocytes?
Leave the blood and mature into macrophages
What are the functions of Leukocytes aka WBCs,
Eosinophils
Toxic to parasites, some phagocytosis
What are the functions of Leukocytes aka WBCs,
Basophils
Produce histamine
What are the functions of Leukocytes aka WBCs,
Neutrophils
Phagocytic
What are the functions of Leukocytes aka WBCs,
lymphocytes
Involved in specific immunity
Natural killer lymphocytes (NK cells): secrete toxins onto the surface of virally infected cells and tumors
What are the functions of Leukocytes aka WBCs,
monocytes
phagocytic as mature macrophages
fixed macrophages in lungs, liver, bronchi
wandering macrophages roam tissues
What are macrophages?
Phagocytic cells of the second line of defense
All macrophages (plus monocytes attached to endothelial cells) = mononuclear phagocytic system
What is the purpose of the differential white blood cell count test?
Can signal signs of disease
-Allergies or parasitic worm infection: increased eosinophils
-bacterial diseases: often show increase in leukocytes and in neutrophils
-viral infections: show increase in lymphocytes
What are wandering macrophages?
Leave the blood via diapedesis
Phagocytize throughout the body
What are fixed macrophages?
Do not move throughout the body
Often phagocytize within a specific organ
- include Langerhans cells (epidermis), alveolar macrophages (lungs) microglia (central nervous system), Kupffer cells (liver)
Second line of defense:
phagocytosis
Phago: eat
Cyte: cell
Ingestion of microbes or particles by a cell, performed by phagocytes
Second line of defense
Inflammatory response
-Redness
-Pain
-Heat
-Swelling (edema: leakage of fluid into tissues)
-Acute-phase proteins activated (complement cascade , cytokines, kinins)
-Vasodilation (histamine, kinins, prostaglandins, leukotrienes)
-Margination and emigration of WBCs
-Tissue repair/scarring
What is the second line of defense?
Operates when pathogens succeed in penetrating the skin or mucous membranes
nonspecific defense:
-composed of cells, antimicrobial chemicals, and processes
-many of these components are contained or originate in the blood
-no physical barriers
What are the phases of phagocytosis?
- Chemotaxis and adherence of microbe to phagocyte
- Ingestion of microbe by phagocyte
- Formation of a phagosome
- Fusion of the phagosome with a lysosome to form a phagolysosome
- Digestion of ingested microbe by enzymes
- Formation of residual body containing indigestible material
- Discharge of waste materials
What are the major events in inflammatory response?
- Injury/immediate reactions
- Vascular reactions
- Edema and Pus formation
- Resolution/ Scar formation
What is diapedesis?
Passage of blood cells through intact blood vessel walls
Second line of defense
What are interferons (IFNs)
Protein molecules released by host cells, appear later in the course of infection
-nonspecifically inhibit the spread of viral infections
-particularly effective against RNA viruses
-cause many symptoms associated with viral infections
Alpha IFN (by epithelium and leukocytes & Beta IFN (by fibroblasts)
-cause cells to produce antiviral proteins that inhibit viral replication
-present early in the infection
Gamma IFN (by T cells and NK cells)
-causes neutrophils and macrophages to phagocytize bacteria
What are the benefits of fevers?
Enhances the effects of interferons
Inhibits growth of some microorganisms
May enhance the performance
-of phagocytes
-cells of specific immunity
-and the process of tissue repair
What is a fever?
Abnormally high body temperature
Nearly universal symptom of infection
Hypothalamus normally set body temperature at 37 C.
Pyrogens (ie endotoxin) cause phagocytes to release interleukin-1
-hypothalamus releases prostaglandins that reset the hypothalamus to a high temperature
-body increases rate of metabolism and shivering to raise temperature
-when IL-1 is eliminated (degraded by enzymes) body temperature falls
Crisis: shaking chills, falling body temp, intense sweating, low BP, may result in death
Alpha IFN (by epithelium and leukocytes & Beta IFN (by fibroblasts)
-cause cells to produce antiviral proteins that inhibit viral replication
-present early in the infection
Gamma IFN (by T cells and NK cells)
-causes neutrophils and macrophages to phagocytize bacteria
What is interferon therapy?
Interferon is not virus specific
Synthesis in response to one cell type will also protect against other cell types
Produced industrially as a treatment for virus infections
Many viral infections don’t respond to interferon therapy at all
Only a slight effect is seen with those viral infections that do respond
Second line of defense
Complement system
The system that enhances (complements) immune reactions
Serum proteins activated in a cascade: more than 26 proteins
Effects of complement activation:
- Opsonization: enhanced phagocytosis
-Membrane attack complex (MAC): cytolysis
- Trigger inflammation
What are some bacteria that evade the complement system?
Capsules prevent C activation
Surface lipid-carbohydrates prevent MAC formation
Thick peptidoglycan makes it harder for MAC to form
Enzymatic digestion of C5a
Interferons:
Protein molecules released by host cells, appear later in the course of infection
-nonspecifically inhibit the spread of viral infections
-particularly effective against RNA viruses
-cause many symptoms associated with viral infections
