BIOL10002 Lecture Notes - Lecture 25: Adaptive Immune System, Cytotoxic T Cell, Natural Killer Cell
Lecture 25: Immune system
Key concepts:
● animals use innate and adaptive mechanisms to defend themselves against pathogens
● innate defenses are non-specific
● the adaptive immune system response is specific
● the adaptive humoral immune response involves T-cells and their receptors
● pathogens are harmful organisms and viruses
Innate and Adaptive Immune Systems interact to remove pathogens
Pathogens: harmful organisms and viruses; there are e.coli that are
good and some that are bad, something that initiates an immune
response
● protists, worms, e.coli, bacteria
Immunity: the ability to avoid disease when invaded by a pathogen
Phagocytes: cells that engulf bacteria or antigen
Phagocytosis: (in the immune system): ability to eat/engulf pathogens,
apoptotic (dying cells) or necrotic/dead cells
Effector cell: relatively short-lived activated cell that defends the body
in an immune response, B-cells or T-cells
Proliferation: rapid increase in the number of something
Antigen: a toxin or other foreign substance which induces an immune
response in the body, especially the production of antibodies
Multipotent: relating to cells that are capable of differentiating into a
range of cell types
Innate immunity: functions as the first line of defense
● consists of soluble factors such as complement proteins, and
diverse components including granulocytes, mast cells,
macrophages, dendritic cells and natural killer cells
● non-specific, typically very rapid response
● involves recognizing components that are common to many
pathogens, 0-4 hours - only after four hours will adaptive
response be initiated
Adaptive immunity: able to distinguish between your healthy cells and
abnormal cells and molecules not from you
● typically slow to develop & long lasting
● involves recognizing components that are specific to each
pathogen
● manifests as increased antigenic specificity and memory
● consists of antibodies, B-cells, and CD4+ and CD8”
lymphocytes
● natural killer T cells and B cells are cytotoxic lymphocytes that
straddle the interface of innate & adaptive immunity
mast cells (innate): found surrounding blood vessels and nerves in the
connective tissue of most organs, and in boundaries between
internal/external environment; secrete histamines, prostaglandins &
tumor necrosis factor
macrophages (innate): have function in the innate & adaptive immune
systems, engulf and digest pathogens, cellular debris, and infected cells,
can move through leaky blood vessels to site of damage, secrete
defensins (molecules that poke holes in cell wall of bacteria, killing cell
by cell lysis) & nitric oxide to kill pathogens after engulfing them
Bone marrow→multipotent hematopoietic stem cell→lymphoid
progenitor cell→able to give rise to many cell types, including
leukocytes (WBC’s): involved in defending the body against infection
and help repair damaged tissue
B-lymphocytes (adaptive): type of lymphocyte involved in antibody
production
T-lymphocytes (adaptive): type of lymphocyte which releases cytokines
to coordinate the immune system & antibody production
lymphocytes: Within immune system, derived from common lymphoid
progenitors; composed of B-cells & T-cells which are white blood cells;
6-15um, 20-50% differential leucocyte count, develop in 1-2 days
Progenitor: an ancestor or parent
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Antibody: protein mainly produced by plasma cells (B-cells) used in the
immune system to neutralize pathogens
Lymphoid: adjective, relating to tissues responsible for producing
lymphocytes & antibodies, occurs in lymph nodes, thymus, tonsils &
spleen
Human lymphatic system:
Thymus: receives immature T-cells from bone marrow, they mature
here due to thymosin which stimulates development, then they
circulate in blood & lymph
Lymph node: small, round structures at many sites along the lymph
vessels & contain WBC’s & leukocytes; many cells, contain memory B-
cells & T-cells, if there is a pathogen in a lymph node, you are in the
adaptive response phase
Spleen: an abdominal organ involved in the production and removal of
blood cells in most vertebrates and forming part of the immune system
Lymph vessels: thin-walled vessels structured like blood vessels, that
carry lymph
B-cells & T-cells made in the bone marrow but T-cells mature in the
thymus, B cells mature in bone marrow
Bone marrow: source of production of B & T-cells, soft, blood forming
tissue that fills cavities of bones & contains fat & immature blood cells
Relationship between plasma & lymph:
● Plasma: fluid remaining when WBC, RBC & platelets removed,
fluid of blood, considered connective tissue of blood, 90%
water, 10% proteins, hormones, electrolytes, nitrogenous
waste, nutrients
● plasma & lymph have similar composition but plasma
contains both white and red blood cells, and lymph contains
no RBC’s
● Lymph: colourless fluid that circulates the lymphatic system,
passes through lymph nodes, filtered & inspected for non-self
molecules/pathogens, made of white blood cells
(lymphocytes) and fluid containing proteins & fats
Interactions between innate and adaptive defence systems
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Document Summary
Key concepts: animals use innate and adaptive mechanisms to defend themselves against pathogens innate defenses are non-specific. Pathogens are harmful organisms and viruses the adaptive immune system response is specific the adaptive humoral immune response involves t-cells and their receptors. Innate and adaptive immune systems interact to remove pathogens. Innate immunity: functions as the first line of defense. Consists of soluble factors such as complement proteins, and diverse components including granulocytes, mast cells, macrophages, dendritic cells and natural killer cells. Non-specific, typically very rapid response involves recognizing components that are common to many pathogens, 0-4 hours - only after four hours will adaptive response be initiated. Adaptive immunity: able to distinguish between your healthy cells and abnormal cells and molecules not from you typically slow to develop & long lasting involves recognizing components that are specific to each pathogen. Manifests as increased antigenic specificity and memory consists of antibodies, b-cells, and cd4+ and cd8 lymphocytes.
