Innate & Adaptive Immunity

Year 2 Pathology - Immunology

Which cell do all white blood cells originate from?

haematopoietic stem cell

What are the 2 key differentiations of haematopoietic stem cells?

common myeloid progenitors

common lymphoid progenitors

Which cells develop from common lymphoid progenitors?

B-cells

T-cells

NK-cells

Which cells develop from common myeloid progenitors?

erythrocytes

platelets (from megakaryocytes)

neutrophils

eosinophils

basophils

macrophages (from monocytes)

What are the 6 main differences between innate and adaptive immunity?

innate is constitutive, adaptive requires priming by antigens

innate responds much faster than adaptive

innate is relatively non-specific whereas adaptive is highly specific

innate has no memory response whereas adaptive does

innate does not get more effective upon second exposure, whereas adaptive does

innate response keeps the infection under control until the adaptive immune response kicks in (innate acts first)

What are the 3 main forms of the first line of innate defence?

mechanical

molecular/cellular

microbiological and environmental

Which features make up mechanical innate immunity?

body surface

cilia in respiratory tract

air movement in the respiratory tract

flushing by liquids

mucus barrier

Which features make up physiological innate immunity?

pH changes and extremes in locations in the body

pyrexia (fever) kills some infectious agents

Where are monocytes found?

bloodstream

What is the function of monocytes?

very limited phagocytosis

precursor cells for macrophages

What is the lifecycle of a monocyte?

circulate the bloodstream for a few days until they migrate into tissues to become macrophages

Where are macrophages found?

in tissues of all organs

What are the functions of macrophages?

strong and sustained phagocytosis - destroy pathogens and clean debris

present antigens to T cells

tissue surveillance

Where are neutrophils found?

bloodstream

What is the lifecycle of a macrophage?

differentiate from monocytes in tissues and live for months to years in these tissues performing phagocytosis and tissue surveillance

What is the function of a neutrophil?

a very strong rapid burst of phagocytosis (first responder)

What is the lifecycle of a neutrophil?

enter the blood after being produced and are rapidly recruited to tissues to perform phagocytosis for hours-days

Where are basophils found?

circulating the blood

Where are eosinophils found?

in tissue during infection or blood when healthy

Where are mast cells found?

in tissues

What is the function of basophils?

to amplify allergic responses

to recruit eosinophils

Which features make up molecular innate immunity?

defensins

lysozyme and sweat gland secretions

myeloperoxidase system

acute phase proteins

complement system

interferons

What are defensins?

small antimicrobial proteins found in many tissues and cells which bind to the membranes of bacteria, fungi and viruses

What are lysozymes?

a family of enzymes which attack the peptidoglycan cell walls of bacteria

Where are lysozymes secreted from?

white blood cell granules

from epithelial cells into tears, saliva, mucus

from sebaceous glands into sebum

What is myeloperoxidase?

an enzyme found mainly in lysosomes in granulocytes and macrophages which kills bacteria and other pathogens by producing toxic hypochlorite and singlet oxygen

How do commensal bacterial contribute to innate immunity?

they inhabit mucosal surfaces and prevent the attachment of pathogenic bacteria which prevents their invasion and infection

Which environmental factors contribute to the innate immunity of an animal?

diet

temperature

humidity

form of immunodeficiency

Which 2 key cells create adaptive immunity?

T cells and B cells

What is an antigen?

any molecule that can bind specifically to an antibody or antigen receptor

What is an epitope?

a short peptide on an antigen which is recognised by an antibody or an antigen receptor

What is an antibody?

a protein that binds specifically to a particular substance (its antigen)

What is an immunogen?

an antigen that can induce antibody production when it binds to its specific antibody or antigen receptor

Which 3 stages of defence must a pathogen overcome to cause disease in an animal?

1. physical barriers

2. innate immunity

3. specific immunity

What type of pathogen is targeted by monocytes?

initial invading pathogens in small numbers

What type of pathogen is targeted by macrophages?

all pathogens

What type of pathogen is targeted by neutrophils?

bacteria and some fungi

What type of pathogen is targeted by basophils?

helminths and allergens

What type of pathogen is targeted by eosinophils?

helminths

What type of pathogen is targeted by mast cells?

parasites and allergens

What is the lifecycle of a basophil?

short lifespan spent circulating blood

What are the functions of eosinophils?

to kill helminths

to contribute to allergic responses

What is the lifecycle of eosinophils?

they circulate the blood for days to weeks until they are recruited to tissues during infection

What are the functions of mast cells?

to trigger local allergic reactions and anaphylaxis

to defend against parasites

What is the lifecycle of mast cells?

they reside in tissues for a long time

What are the features of monocyte granules?

few present

What are the features of macrophage granules?

contain lysosomes with digestive enzymes

What are the features of neutrophil granules?

many toxic granules

What are the features of basophil granules?

contain histamine and heparin

What are the features of eosinophil granules?

contain major basic protein and eosinophil peroxidase which is toxic to parasites

What are the features of mast cell granules?

contain histamine, proteases and cytokines