CH. 23 Innate Immunity Flashcards
What is meant by the term “human microbiota”? Where are microbes found on/in the body? Where should they not be found? What does it indicate if microbes are found in these latter areas?
Human microbiota is the collection of all microbes associated with the human body
Microbes are found in areas that are exposed to the external environment (ex. skin, oral, & nasal cavities, lungs, etc.)
They should not be found in sterile areas (ex. blood, most internal organs, etc.) which signals infection in that area
What are some microbiota interaction relationships?
Commensalism microbes: does not harm or benefit the host but benefits microbes
Mutualistic microbes: benefits both host and microbes
Parasitic microbes: harm the host but benefits the microbes
What are the risks & benefits of having a microbiota?
Benefits:
-Interfering with pathogen colonization producing immunomodulatory proteins
-Metabolizing food that the host cannot process
-Producing vitamins that the host cannot make
-Honing our immune system
Risks:
-Dysbiosis of the microbiome can contribute to infection, obesity, and inflammatory and autoimmune diseases
What are the features of those locations that harbor
microbes (i.e., skin, oral/nasal area, stomach, intestines, GU tract)?
There are more microbes on/in your body than your own cells. It is split between aerobes: anaerobes ratio
Skin - 1:10
Mouth - 1:10
GU Tract - 1:100
GI Tract - 1:1000 (highest number of microbes)
Skin: sweat glands, acquired by birth canal and birth environment
Mouth: vagina, uterus, acquired by birth canal by caregiver
GU Tract: acquired by surrounding external environment
GI Tract: acquired by baby formula by mother or caregiver
What are opportunistic pathogens? What is microbial antagonism?
Opportunistic pathogens are microbes that normally is not pathogenic but can cause infection or disease in an immunocompromised host organism
Microbial antagonism is the inhibition of one bacterial organism by another due to competitive exclusion
What are the different divisions of the immune system? What are the features of each?
First Line of Defense (innate immunity):
-Intact skin
-Mucous membranes & their secretions
-Normal microbiota
Second Line of Defense (innate immunity):
-Phagocytes (neutrophils, eosinophils, dendritic cells, and macrophages)
-Inflammation
-Fever
-Antimicrobial substances
-Complement
Third Line of Defense (adaptive immunity):
-Specialized lymphocytes: T & B cells
-Antibodies (stimulated by the presence of antigen)
What are the cells that make up the immune system and what is their function? Where do they originate from?
They are known as various white blood cell types called leukocytes. There are two types of leukocytes: granulocytes & agranulocytes
What are granulocytic leukocytes? List them out and their features and how much there are in the blood
Neutrophils (polymorphonuclear leukocytes) - 70%:
phagocytic; active in initial stages of infection
–can exit blood & enter infected tissue
Basophils - 1%: release components promoting
inflammatory & allergic responses (histamine)
Eosinophils - 3-5%: phagocytic & exit blood; release toxins. Also deal with large multicellular pathogens.
What are agranulocytic leukocytes? List them out and their features and how much there are in blood
Total of 25% of agranulocytic leukocytes in blood
Monocytes: differentiate into macrophages and dendritic cells in lymphatic tissues
-Are phagocytic cell types
-Are also antigen-presenting cells (work with adaptive immune system)
Lymphocytes: consist of…
-Natural Killer Cells: kill infected body cells & some tumor cells; recognize abnormalities in plasma membrane. When bind to target, it simulates the secretion of perforins to cause lysis
-T Cells (intracellular pathogens): moderate specific immune response
-B Cells (extracellular pathogens): produce antibodies to bind antigens
What is the lymphatic system?
Part of the immune system where it maintains homeostasis within body fluids and defends the body against infections
Features:
-Spleen, tonsils, small intestine
-Protect against inhaled ingested microbes
-Contain T cells, B cells, dendritic cells, macrophages
Gut-associated lymphoid tissue (GALT) of the GI tract -> Peyer’s patches contain specialized M cells that take up microbes from the intestine and release on the other side for macrophages
Skin-associated lymphoid tissue (SALT) provides skin with immune surveillance that protects against infection with intracellular pathogens
What are major histocompatibility complex (MHC)? What are the classes and features?
MHC is a set of proteins on the cell surface that are responsible for how identifying cells as your own
MHC Class II (antigen-presenting cells): macrophages, dendritic cells, B cells
MHC Class I (nucleated mammalian cells): all other cells that are not class II are type I
How do the physical barriers (skin, mucous membranes, lungs, GI tract) prevent infection?
The skin is composed of the epidermis and dermis
-Has a protective keratin layer on the epidermis
The mucous membranes line the GI, GU, & respiratory tracts of the epithelial and connective tissue layers
-Mucus traps the microbes and moisten surfaces
-Tears & Saliva prevent the colonization of microbes
-Hairs (nose) & Cilia (respiratory tract) trap microbes
-Epiglottis, Earwax, & Digestion eliminates microbes
What is detection by toll-like receptors?
Toll-like and NOD-like receptors are receptors located on the outside of the plasma membrane that helps in detecting invading pathogens. These receptors are able to recognize MAMPs or PAMPs that are located on pathogens (tag them as foreign). If MAMPs/PAMPs are recognized by the toll-like receptors, they induce the host cell to release cytokines to activate immune cells
What are chemical barriers to infection?
Skin: sebum (oily secretions) forms a film on the skin
-Contains fatty acids to lower pH to prevent colonization of pathogens
-Perspiration: high salt, contain lysozyme to degrade polypeptidoglycan (in tears and saliva)
Mucous Membranes:
-Saliva: lysozyme, urea, uric acid, antibody
-Gastric Juice (Stomach): pH 1-3 due to HCL
-Vaginal Secretions: acidic pH
-Urine: lysozyme & pH 6
Defensins: small, antimicrobial, cationic peptides produced by many human cells; destroy invader’s cell membrane (INNATE ONLY)
What is the acute inflammatory response? What is the overall objective of this process? What are some of the important cytokines involved in this process and what do they do?
The introduction of microbes causes infection. This raises inflammation to cause extravasation (provides a way for the body’s phagocytic cells to gain access to infected sites) with the help of vasoactive factors to increase vascular permeability, which then releases cytokines and chemoattractants to fight off the infection
Some important cytokines are bradykinin and histamine:
-Bradykinin promotes extravasation, stimulates the release of prostaglandins to stimulate nerve endings (inflict pain), & stimulates mast cells to degranulate to release histamine
-Histamine stimulates vessels to open further for blood plasma and platelets to be released into an area
