First line of defence flashcards

INTRODUCTION AND FIRST LINE OF DEFENCE

  • Outline the overall organisation of the immune system: lines of defence and innate vs adaptive responses

innate immune response (non-specific)= does not attack the host’s body, specifically attacks those invading organisms, often innate cells are detecting prokaryotic cells which they distinguish from our own eukaryotic cell line, response is the same no matter how many times u see an organism

adaptive immune response (specific)= will change and remember previous interaction with same organism,

in reality there is a significant amount of overlap between the different parts of the immune system (they don’t behave as secrete parts)

define key terms

  • Allergen = any invading entity that is otherwise harmless to the body but generates an immune response and therefore can potentially cause harm to the body (e.g. people with hay fever having an inappropriate immune response to what would otherwise be a harmless protein such as grass pollen)

  • Pathogen = an invading organism that can potentially cause harm to the body and generate an immune response

  • Immunogen = anything that generates an immune response (can be either an allergen or pathogen as they are both examples of immunogens)

  • Antigen = the specific component of the immunogen that elicits the immune response (e.g the spike on a COVID virus, particular protein on surface of bacteria)

  • Epitope = the explicit amino acid sequence that is causing an immune response, usually the amino acid sequence that the antibodies are binding to when the immune response is elicited

  • Hapten = a potential immunogen, its a substance which can potentially evoke an immune response but it is not strong enough by itself to actually do so (e.g. a vaccine)

  • Adjuvant = something that non-specifically increases the immune response, can also be used in immunogens (many pollutants such as smoking can act as adjuvants enhancing the immune response which is why smoking is often associated with increased incidence of allergy- more likely for an inappropriate immune response)

Cytokines

Leukotrines

Prostaglandins

Chemokines

  • Immunological redundancy = is the ability of the immune system to respond in multiple ways (overtime we have developed several different ways of combating the same pathogen which means that if one part of the immune system stops working theres usually another part that can carry on working so we don’t become immunodeficient) —> this great for us but also makes it difficult for scientists to understand and predict what is going to happen

  • Memory = our immune system has immunological memory associated with the adaptive immune response which means the first time we encounter a pathogen we will evoke a primary immune response. But our immune system will remember what that organism looked like and what worked and didn’t work so it will refine itself so that the second and third time to receive the same entity we will have a much stronger immune response i.e. the secondary immune response.

discuss the four components of the first line of defence with examples

  1. physical and mucosal barrier =

skin

~ largest organ in the body and presents a tough anatomical barrier to the external environment

~ lack or water and basic nutrients making it difficult for invading organisms to survive

~ each cell is joined with tight junctions that effectively seal it off making it difficult to penetrate the surface

~ range of epithelial membranes separate your body from the external environment and potential invaders

mucosal membranes

~ the lining of airways, digestive tract, reproductive tract and vascular systems often get coated with glycoproteins called mucins

~ hese mucosal membranes are thick and sticky and really good at trapping organisms preventing attachment and replication

  1. mechanical =

tears

~ help to flush out invading organisms

urine

~ flush out invading organisms with extra force, expelling pathogens from the body

~ urine helps flush out the reproductive tract and urinary tract (one of the reasons sexually transmitted infections are less common in men is because the urinary tract is the same thing as the reproductive tract and urine helps flush out both of those systems)

saliva

~ helps to dilute organisms making them more difficult for them to group together for protection

membranes

~ covered in cilia and or undergo peristalsis which helps to flush out trapped organisms before they can gain a foothold in the body

  1. commensal microbiota

~ these are the good bacteria and parasites that are found all over the body , both on the outside and inside

~ compete with potentially pathogenic invaders for nutrients and epithelial attachment sites

~ more direct benefits include, stimulating production of antimicrobial peptides at our epithelial membranes

~ in order to defend themselves from competitors such as pathogenic invaders, commensal microbiota often produce their own antimicrobial substances which indirectly defend the body

~ e.g vaginal lactobacill produce lactic acid increasing the pH and making the vaginal environment more difficult to inhabit by pathogens

  1. chemical

~ our bodies produce a range of chemicals that provide natural defence against a broad range of potential invaders

~ this can be simple as the extreme pH levels found around our body e.g. in the urogenital cavities

~ invaders of gastrointestinal tract have it even more difficult as they have to be able to survive both extremes: strong acids in the stomach following the strong alkaline in the intestines

~ GI tract provides a range of digestive juices e.g. bile salts that aim to break down a whole range of biological materials such as fatty acids, carbohydrates and proteins

~ range of soluble mediators e.g. lysozymes that attack and breakdown bacterial cell walls, present is many of our fluids including blood, tears and epithelial secretions