Unit 6- Response To Infection Flashcards
What cells are responsible for phagocytosis? 3
Phagocytes: neutrophils, monocytes and macrophages
How have phagocytes adapted?
Complex cytoskeleton that allows them to change shape
Contain lysozymes
Large
Describe phagocytosis:
- phagocytes move through blood/tissue fluid in response to chemicals
- they surround and engulf the foreign body (phagocytosis)
- microbes are trapped in phagosome which fuses with lysosome
- the lysozymes hydrolyse the microbe proteins, carbs and fats
Where do the different phagocytes work?
Neutrophils -blood
Macrophages and monocytes - tissue fluid/lungs and other spaces
What causes inflammation?
Granulocytes release chemicals (prostaglandins and histamines) which stimulates inflammation
What changes occur in inflammation? Name 4
- vasodilation
- capillary leakage (so phagocytes and granulocytes can enter)
- sensory neurone impulses (tender areas)
- blood clotting
- fever (the heat kills more pathogens than human cells)
- tissue repair (collagen deposits and stimulation of new cell growth makes scar tissue)
What make up the non-specific immune response?
Phagocytosis and inflammation
What cells make up the specific immune response?
B-lymphocytes and T-lymphocytes
How do we know the specific immune response is a later evolutionary advancement?
Only vertebrates have it as the cells that are involved are made in the bone marrow
What are antigens?
Clue: antigen is short for (ANTIbody GENerators)
Large molecules that bind to lymphocytes triggering a specific immune response
Which cell makes antibodies?
B-lymphocytes
What is an antibody?
A protein molecule that can bind specifically to an antigen
Structure of an immunoglobulin:
4 polypeptide chains (2 heavy and 2 light chains)
Joined by disulphide bonds to form a Y shape
They all have the same constant region (stem) and different variable regions (different amino acid sequences)
Which leads to a highly specific antigen-antibody complex
What is self recognition?
When cells are able to recognise the cell is not foreign by the distinct marker proteins (MHCs) on the cell membrane
What are receptors and where are they found?
They are proteins witch only 1 binding site (unlike antibodies 2) found on surface of T-lymphocytes
What do receptors do?
They bind to specific antigens forming an antigen-receptor complex
What is the main antigen presenting cell?
Macrophage phagocytes as they are in largest abundance
What is the macrophages role in the first step of infection from antigens?
In order to initiate the specific immune response a macrophage needs to engulf the pathogen and present the antigen on its surface becoming an antigen-present cell
What are cytokines and what cell releases them?
They are chemicals which stimulate clonal selection, released from macrophages and T-helper cells
Describe clonal selection from antigen presenting cell:
Eventually a helper T cell with a complementary receptor to the antigen will bind to antigen
The T helper cell releases cytokines which stimulate immature T and B lymphocytes to activate, proliferate and differentiate
The activated cells divide by mitosis making a clone army of cells with identical binding sites that is specific to the foreign antigen
How do T killer cells kill the infected cells?
- bind to antigens on infected cells
- secrete porin proteins
- porin makes pores in the cell membrane so water diffuses in
- the infected cell bursts (lysis)
What cells are part of cellular immunity?
Cytotoxic/killer T cells and memory T cells
Which cells are part of the humoral immunity?
B-lymphocytes which differentiate into thousands of plasma cells
Memory B cells
What is the job of plasma cells?
To synthesise antibodies specific to the antigens
