12.5: non-specific animal defences against pathogens?

What are the two lines of defense against invasive pathogens that mammals have?

Non specific immune response and the specific immune response

What is cytokines?

Chemicals released by WBC which act as a cell signalling molecule informing phagocytes that the body is under attack and stimulates them to move to the site of infection/inflammation

What are mast cells?

Immune cells that are activated by damaged tissue. They release histamine and cytokines

What’s Major histocompatibility complex?

Proteins found on the surface of cells that help the immune system recognise foreign substances

What is opsonin?

Chemical that bind to pathogens and ‘tag’ them so they can be easily recognised by phagocytes

What are antigen presenting cell?

A cell that presents fostering antigen to immune cells to stimulate an immune response

What are the primary defences?

Skin, mucous membranes, chemical secretions (lysosomes and hydrochloric acid in the stomach) expulsive reflexes (such as coughing)

What happens when platelets come into contact with collagen?

They stick together and begin secreting several substances (clotting factors)

The blood clotting cascade

Damaged cells → platelets activated → thromboplastin(enzyme) + Ca + prothrombin (protein) → thrombin (enzyme) + fibrogen(soluble) → fibrin (insoluble) → forms clot

What does seretonin do?

It makes the smooth muscle in the walls of the blood vessel contract and narrows them? Reducing blood supply to the area.

What happens when the blood clot dries out?

It forms a scab, the epidermal cells below the scab grow sealing the wound and damaged blood vessels regrow. Collagen fibres are deposited to give new tissue strength.

What do histamine do during the secondary non specific defence?

It dilates the blood vessel and causes more plasma to move into tissue fluid. This raises the temperature and caused localised swelling to isolate the pathogen. Excess tissue fluid drains into the lympathic system and transported into the lymph nodes

What do mast cells do during the non specific defence response?

They are activated in damaged tissue and release chemicals called histamines and cytokines

What do cytokines do during the secondary non specific defence?

They stimulate the hypothalamus to raise the body temperature which reduces the rate of pathogen reproduction. The specific immune system works better at higher temperatures

What are phagocytes?

Specialised white blood cells that engulf and destroy pathogens

What are the two types of phagocytes?

Neutrophils and macrophages

What kinda receptors do phagocytes have?

They have receptors on their cell membrane that bind to common opsonins and the phagocyte then engulfs the pathogen q

What are the stages of phagocytosis?

1) pathogens produce chemicals that attract phagocytes

2) phagocytes recognise antigens

3) the phagocytes engulfs the pathogen in a vacuole called phagosone

4) the phagosone combines with a lysosome to form a phagolysosome

5) enzymes form the lysosome digest and destroy the pathogen

What happens when a macrophage digest a pathogen

It combines antigens from the pathogen with special glycoproteins in the cytoplasm called the major histoconpatibility complex.

The MHC complex moves these pathogens antigen to the macrophage own surface membrane becoming an APC which stimulates other cells in the specific immune response