Core Concepts-L2-Innate Defences

difference between innate and adaptive immunity and cells associated

innate: non specific, have some tolerance, may have memory, instant and immediate: macrophages, phagocytosis, basophils, ILC’s, NK cells

adaptive: specific, 2nd line of defence, protection from re-exposure, T/B cells and antibodies and cytokines

explain the timing of the primary immune response and what is released

1. pre-formed innate- 0-4 hours. recognition of pathogen is broad. compliments, AMP in bodily fluids are always there

2. early induced inflammatory response-4-96hours. resident innate cells detect NAMPs and initiate signalling pathways. make inflammatory mediators: prostaglandins, cytokines, chemokine and complement activation

3. specific adaptive response- 96 hours+. APC will migrate from site of infection to lymph nodes and present. clonal expansion, differentiation into effector T cells and plasma cells. highly specific

what determines what type of immune response is produced?

• how much of the pathogen we were exposed to

• what TYPE of pathogen

• what toxins or virulence factors are present

types of helper T cells and responses

Th1- interferon gamma and activates phagocytic functions- intracellular bacteria

Th2- parasitic infections- stimulates B cells, increases mucus to push out parasites: IL-4, IL-5

Th17- fungal infections- recruits neutrophils, IL-17, IL-22- increase AMP

Tfh- help B cells produce antibodies. interact with B cell germinal centres and make B cells make plasma cells and memory B cells

what are some innate defences?

1. complement system- cascade for serums that opsonise pathogens and recruit immune cells and lyse microbes

2. AMP- cause lysis

3. lysozyme- cleaves bacterial peptidoglycan and weaken bacterial cell walls

induced inflammatory response steps: steps 1-3

1. infection/damage- self or non self

2. responder- macrophages that patrol the body. dendritic cells or epithelial cells. compliment proteins bind to microbes to kill them and instruct inflammation

3. messengers released: cytokines- IL-1, TNF, chemokine gradients- immune cells to the site of infection making mediators like histamine. ——lipids like prostaglandins- mediate inflammation. acts on endothelial cells to make more blood flow and more permeable. clotting to contain infection

induced inflammatory response steps: steps 4-7

4. inflammation recruits cells in a hierarchy of how many are present. neutrophils are the most abundant so come in first due to chemokine. monocytes from the blood and become macrophages. lymphocytes like NK cells and granulocytes release histamine rich granules that amplify inflammation

5. effector functions: phagocytosis, antigen presentation, cytotoxic killing and release of AMPs

6. activation of the adaptive immune response: when APC get to lymph nodes- leads to expansion of T/B cells

7. resolution of inflammation-M1 macrophages(are pro) and M2 macrophages are anti inflammatory and are tissue repairing.

routes of invasion of microbes into the body and examples of each

1. inhalation- TB

2. direct contact- HIV

3. invasion- tissue damage- plasmodium from mosquito

4. ingestion- through mouth into the GI tract- salmonella

describe anatomical barriers in the immune system

anatomical barriers: s

1. skin-has layers of fats and epithelial cells. produces AMPs.

2. mucosal surfaces- need to allow gas exchange and nutrient absorption- has mucin to trap microbes, ciliated epithelial cells- move mucous mucosa has tight junctions- Claudius,

3. JAMS-junctional adhesion cells- allows the migration of cells such as immune cells

types of barriers in the immune system

1. anatomical barriers

2. chemical barriers

3. microbiota barriers

describe chemical barriers in the immune system

• may be pre-formed but increase after infection

• lysozyme: breaks down peptidoglycan and bacterial cell walls(positive)- breaks sugar beta1,4 linkages

• AMPs- target microbial cells and causes pores and lysis- found on skin/mucosal surfaces. defensives(skin), cathelicidins(gut), lecticdins(lungs)

describe microbiota barrier

• bacteria on the skin etc

• co evolved with the body

• produce beneficial metabolites like short chain fatty acids- butyrate, propionate, acetate