Immune System Flashcards
Purpose of the Immune System
To protect the body against harm (caused by infection) of small microorganisms called pathogens
Natural barriers against infection
Skin: a physical barrier which secretes antimicrobial substances
blood clotting: seals wounds to prevent infection
Phagocytosis: engulfs and digests any foreign bodies in the blood
Inflammation: helps to isolate foreign substances and prevents further contact with the body
Mucus: mucous membranes of the respiratory system release mucus to waft mucus inhaled
Lysozymes: found in tears, saliva and stomach acid which kill bacteria
Phagocytosis
-Phagocyte recognises foreign antigens & receptors bind to it
- cytoplasm moves around and engulfs the pathogen (it’s now present as a phagosome)
- A lysosome fuses with the phagosome to form a phagolysosome
- Lysozymes hydrolyse the pathogen in the phagolysosome
- Soluble debris exists the cell via exocytosis
- Phagocyte displays the pathogens antigen on it’s surface
Inflammation
- At a wound, damaged cells release a chemical (histamine)
- These chemicals caused blood vessels to leak fluid into the tissues leading to swelling
-This helps to isolate and prevent the pathogen from making further contact with the body - They also attract phagocytes (WBC)
Antibody
Proteins synthesised by B cells which are specific to 1 antigen, they bind to form an antigen antibody complex
Aggulation
-antigens bind to two antigens at a given time forming antigen antibody complexs
-this leads to pathogens clumping up (angulation)
-This makes pathogens easier to find and phagocytosis to take place
Cell mediated immune response (T lymphocytes)
Specific (helper) T cells with complementary receptors bind to antigen on antigen presenting cell
This activates the T cells to divide by mitosis, stimulate B cells & phagocytes
Types of T lymphocytes
- Helper T cells: activate B lymphocytes & stimulate phagocytosis
- Cytotoxic T cells: create pores in plasma membrane of pathogens by producing perforin
- Memory T cells: remain in blood until another infection, they then divide rapidly by mitosis
Humoral Response (B Lymphocytes)
- B lymphocyte cells are covered in receptors for their specific antigen
- Once they find the complementary receptor, their stimulated by helper T cells (that release cytokines)
- They differentiate into plasma or memory b cells
Type of B lymphocytes
-Plasma Cells: rapidly produce antibodies which cause antigens to become inactivated
- memory cells: remain in blood circulation (for years) until the same antigen appears, they then rapidly divide by mitosis
Primary vs Secondary exposure
The second exposure produces antibodies faster and at a higher rate, as the antigens are detected and memory cells can rapidly undergo mitosis to produce antibodies
Lag time
The time at the primary exposure when the correct complementary antibody is being found for the pathogens antigens
