innate immune system

What are the 2 main types of immunity

innate

adaptive

what are the major elements of the innate immune system 

• Soluble factors: Lysozyme, complement, acute phase proteins

• Cells: phagocytes, innate lymphoid cells, natural killer cells

what is the role of antibodies in the adaptive immune system

provide antigen specificity and memory

how does the adaptive immune system differ from the innate immune system

adaptive has antigen specificity and memory

what are the two m ain mechanisms of the innate immune system

1. limit entry- skin and membranes

2. Limit growth - phagocytosis and soluble chemical factors

what is the role of skin in the innate immune system

• impermeable to majority of infectious agents 

• hostile environment for many bacteria - lactic acid and FA in sweat and sebaceous secretions, lower pH

how does sweat help in limiting entry of microbes

• has antimicrobial properties

• increases in salt prevents the growth of many bacteria

how does the burn unit prevent serious infections

has positive pressure to prevent entry of pathogen

what is the role of membrane in the innate immune system

• line inner surface of body, secrete mucus

• inhibit bacterial adhesion, inhibit entry

• ciliary action - remove microbe and foreign particles

• flushing action - tears/saliva/urine, protect epithelial surfaces, presence of antimicrobial compounds (acid, spermine and zinc, lactoperioxidase, lysozyme)

what is the function of normal flora in the innate immune system

• suppress growth of pathogenic microbes

• protective layer

• compete for nutrients

• produce inhibitory compounds

what are the two ways to limit growth

1. phagocytosis

2. soluble chemical factors

what are the two type of phagocytes

1. macrophages

2. polymorphonuclear granulocytes - neutrophils

macrophages

• bone marrow - promonocytes

• monocytes - blood

• macrophages - tissues

• concentrated in lung, liver, lining of lymph nodes - well placed to filter off foreign material

polymorphs

• dominant in the blood stream

• share common haemopoietic precursor - all from one kind of cell

• no mitochondria - glycogen is source of energy

• non-dividing, short lived, segmented nucleus

• Granular cytoplasm - enzymes needed to kill engulfed pathogens

what is phagocytosis and its role in the immune system

• process o engulfing pathogens

• involv. phagocytes like macrophages and neutrophils

• key mechanism for limiting growth of pathogens

how to pathogens attach to phagocytes

• by pattern recognition receptors - PAMPs (pathogen-associated molecular patterns) on microbe. PRRs (pathogen-recognition receptors) on phagocyte.

• phagosome formation

• granule fusion and killing - oxygen independent/oxygen dependent

what triggers phagocytosis in phagocytes

attachment to pattern recognition receptors

what does phagocytosis and complement system depended on 

contact dependant

formyl methionyl peptides attract leukocytes - chemotaxis 

complement proteins

what is the complement system’s role in the immune response

it amplifies the immune response through a cascade

what is the most abundant component of the complement system?

C3

what is the advantage of the cascade system 

gradual amplification hence more control pts.

how does the alternative complement pathway function

C3B binds to bacterial surfaces for opsonisation

what happens if there is no C3

immune system severly comprimised

what is the most important protein in complement system

C3 convertase

What is the role of C3 convertase

breaks C3 into C3a and C3B - happens at a low rate when no pathogen

what are the levels of C3 in the body

they are very unstable hence they are in low levels

when does C3 convertase become stable

when microbial polysaccharide attach to enzyme

how does the alternative complement pathway function

C3B binds to bacterial surfaces for opsonisation - tags bacterial cell for phagocytosis

what is C5 protein

forms complex with C3a, chemotactic factor

inc. vascular permeability - allow macrophages to leave blood vessel to reach infection site

what is C5a/c3a complex

acts as chemical signal for inflamation

what do bacterial cells exerts on the membrane

exerts a lot of pressure on the membran

what is C5b

inserts into bacterial membrane to attract other complement proteins

poke hole in membrane

how is the membrane attack complex formed

C5b +C6+C7+C8+ C9 etc.

what are the functions of acute phase proteins in the immune response

• increased concentrations in response to injury/inflammation

• bind to PAMPs and opsonise bacteria

• e.g. C-reactive protein, Mannose binding protein

what are antimicrobial factors

• act within phagocytic cells but also body fluids

• tears and saliva

• lactoferrin

what are interferons and their role in the immune system

• discovered as means of viral interefrence

• they limit viral replication and spread

how do IFNs work

infected cells secrete IFNs - bind to the nearby uninfected cells

IFN causes cells to produce antiviral proteins that interfere with virus replication - limit spread

how do natural killer cells function in the immune system

• bind to virus-infected cells

• release granules like perforin and granzyme B

• induce apoptosis caused by granzyme B

what is the role of eosinophils in the immune system

• combat larger parasite

• binds to c3b which causes activation

• release toxic compounds to damage membranes

• eosinophils dont engulf but rather attach and release antimicrobial stuff