3.2.4 Cell recognition and the immune system Flashcards
What are causes of disease?
Life style - smoking, alcohol, no exercise.
Genetic defect - caused by a mutation in the DNA coding for a protein.
Infection - caused by a pathogen : a microbe (bacteria, fungus, virus or protocista) that causes illness.
How do pathogens cause disease?
Damage host tissues by breaking cell membranes or preventing DNA, RNA and protein synthesis.
Produce toxins e.g. cholera toxin.
What role does lymphatic vessels have in the immune system? + what do they contain?
They contain lymphatic fluid that circulates and removes waste and harmful substances from the body.
What role do lymph nodes have in the immune system? + what do they contain?
They are filters that remove harmful substances.
They contain white blood cells called lymphocytes.
Outline the 1st line of defence
Skin creates a barrier to infection.
Outline the 2nd line of defence
White blood cells (leukocytes) respond non-specifically.
Outline the 3rd line of defence
Specific responses from lymphocytes.
Antigen definition
- A cell-surface molecule which stimulate immune response (Any part of an organism or substance that the immune system recognises as foreign).
- Usually (glyco)protein, sometimes (glyco)lipid or polysaccharide.
- immune system recognises as “self” or “non-self” = enables identification of cells from other organisms of same species, pathogens, toxins & abnormal body cells.
What are the 2 types of the defence mechanism?
Non-specific & specific
What is the non specific defence mechanism and give examples
The response is immediate & always the same e.g. physical barrier, phagocytosis.
What is the specific defence mechanism and give examples
The response is slower & different for each pathogen e.g. cell mediated T-lymphocytes, humoral B-lymphocytes.
What are the physical barriers to infection (1ST LINE DEFENCE)?
- Tears contain lysosome.
- Stomach acid & enzymes.
- Cilia & mucus lining respiratory surfaces.
- Epithelial layer of the skin.
- Platelets - damaged skin (blood clots)
What are the 5 key steps of phagocytosis? How does phagocytosis destroy pathogens? (2ND LINE OF DEFENCE)
1.The phagocyte is attracted to the pathogen by chemicals produced by pathogens (chemotaxis).
2. The phagocyte engulfs pathogen via endocytosis to form a phagosome.
3. Lysosomes migrate towards the phagosome formed by engulfing the pathogen (phagolysosome).
4. The lysosomes release their lytic enzymes into the phagosome, where the pathogen is broken down.
5. The breakdown products of the pathogen are absorbed by the phagocyte are presented on their cell membrane.
What is humoral immunity? (3RD LINE OF DEFENCE) + what does it involve?
Humoral immunity involves B-lymophocytes (B-cells). These are a type of white blood cell and are made and developed in the bone marrow. They are found in bodily fluids e.g. blood, lymph and plasma. They also respond to foreign bacteria & viruses.
Outline the process of Humoral Immunity (B-cells)
- Once phagocytes have engulfed and digested an invading pathogen, some of the antigens from the pathogen are displayed on its surface. This is called ANTIGEN PRESENTATION.
- T helper cells attach to the presented antigens and stimulate B-cells to divide by mitosis.
- The cloned B-cells develop and differentiate into Plasma and Memory cells.
Outline the primary immune response in humoral immunity (PLASMA CELLS)
These are plasma cells which secrete antibodies directly and destroy the pathogen and any toxins. They only live a few days & secrete 2000 antibodies per second.
Outline the secondary immune response in humoral immunity (MEMORY CELLS)
These are memory cells which do not secrete antibodies, they circulate in the blood & tissue fluid and divide rapidly into more plasma cells & memory cells when they encounter the same pathogen again.
Is the quantity of antibodies in the blood lower during the primary or secondary response over time?
Primary response.
What is cell mediated immunity? (3RD LINE OF DEFENCE) + what does it involve?
Cell mediated immunity involves T-lymphocytes (T-cells). These are made in the bone marrow and mature in the thymus. They respond to the body’s own cells altered by cancer, cells infected with viruses & to transplanted tissues.
Outline the process of Cell Mediated Immunity (T-cells)
What is the Cellular Immune Response?
Non-self antigens entering lymph nodes from cancer cells or transplanted organs sensitise T-cells within the lymph nodes. The sensitised T-cells divide rapidly by mitosis to generate large numbers of cloned (identical) T-cells.
What do the cloned T-cells do?
They mature and differentiate into cells that do different jobs.
What are two of the cells T-cells mature and differentiate into? + function of each
- TC Cells (Cytotoxic T-Cells) kill virus infected cells or cancerous cells by making holes in their membranes.
- TH Cells (Helper T-cells) stimulate B-lymphocytes to divide.
5 quick questions -
1. An enzyme found in white blood cells that digests pathogens.
2. Type of acid found in the stomach.
3. Type of immunity where antibodies are made.
4. Name of the white blood cells that produce antibodies.
5. Name of the blood cells that engulf pathogens.
- = Lysosomes.
- = Hydrochloric acid.
- = Active.
- = B-cells - Plasma cells.
- = Phagocytes.