Response to infection (6.7–6.9, 6.12–6.13) Flashcards
lysis
the bursting of a cell
antigens
Foreign material that invades the body
What are the 4 non specific immune system responses?
Lysozyme, inflammation, phagocytosis and antimicrobial proteins
How do lysozymes protect against pathogens?
found in tears they kill bacteria by breaking down their cell walls. Also found in saliva and nasal secretion.
How does inflammation occur?
The damaged white blood cells release special chemicals eg histamine. Causing the arterioles in the area to dilate and increasing the permeability of the capillaries. Plasma fluid, white blood cells and antibodies leak from the blood into the tissue causing oedema.
Phagocytes
white blood cells that engulf antigens. Inc neutrophils and macrophages.
phagocytosis
when phagocytes engulf and destroy antigens.
How do antimicrobial proteins provide a defence against pathogens?
They diffuse into the surrounding cells where it prevents microbes from multiplying. It inhibits microbial protein synthesis.
What are the two main types of lymphocytes?
T cells and B cells
Where are B cells produced?
bone marrow
Where are T cells produced?
thymus
What are immunoglobulins?
antibodies
What bonds hold the peptide chains of a T cell?
Disulphide bonds
Explain what happens in the activation of T helper cells
Bacterium with antigen on surface is engulfed by macrophage. Macrophage presents antigens on its surface and becomes an APC. The APC eventually find the T helper cell with the complimentary CD4 receptor. Clonal expansion occurs and the T helper cell activates and divides into more T memory cells and T helper cells.
Explain what happens in clonal selection
Bacterium binds to B cell with complimentary receptor. The B cell becomes an APC. The activated T helper cell with a complimentary receptor binds to the APC (B cell) and produces cytokines that stimulate the B cell. The B cell divides to give B memory and B effector cells. The B effector cells differentiate into plasma cells. The plasma cells secrete antibodies which bind to the antigens.
Explain what happens once the antibodies are produced by the B cell
Antibodies bind to the bacteria with antigens on the surface and label them. Antibodies bind to the antibody receptors on a macrophage. The macrophage engulfs the antibodies and bacterium. Lysosomes fuse with the vacuole releasing the digestive enzymes that destroy the bacterium.
Explain the role of T killer cells
A bacterium infects cell of host.
The cell presents the antigen and becomes an APC.
T killer cell with a complimentary receptor binds to the APC.
Cytokines stimulate the differentiation of the T killer cell into T killer memory cells and active T killer cells.
The clones of the active T killer cells bind to infected cells presenting antigens.
T killer cell release chemicals that cause pores to form in the infected cell, causing lysis.
The infected cell dies.
How can one gene give rise to more than one protein?
Through post transcriptional changes to mRNA. The introns are removed leaving only the exons. This is mRNA. Before this it is called pre-mRNA when introns were still present. Once the introns are removed the exons can be spliced in many different ways leading to more than one protein.
What are the 3 ways the body is protected from infection?
Skin, stomach acid, and gut and skin flora.
How does the skin protect the body?
tough physical barrier consisting of keratin
How does stomach acid protect the body?
kills bacteria ingested
How does gut and skin flora protect the body?
natural bacterial flora competes with pathogens for food and space.
What is an example of natural passive immunity?
the crossing of mother’s antibodies through the placenta and/or breast milk
What is an example of natural active immunity?
Being exposed to or getting the disease
