Component 3A - The Immune Response Flashcards
How does your body protect you when the skin barrier is breached?
- Blood clotting to seal wounds
- Inflammation to localise breaks in the barrier - raised temperature is unfavourable and large amount of blood flow brings lots of phagocytes
How does the skin resist infection and how is it maintained?
• The skin is a tough barrier and vitamin C is needed to
maintain collagen in strong connective tissue
How does skin flora resist infection?
- Skin flora offer protection by competing with pathogenic bacteria and unlike these bacteria, the flora is not easily removed by washing
- This means regular washing is a good way of resisting infection
How does the body resist infection when microbes enter the blood stream or are breathed in?
• Phagocytosis to destroy invading microbes
• Ciliated mucous membranes that trap microbes in
inhaled air
What enzyme does the body contain to resist infection?
Lysozyme in tears, saliva and stomach acid that kills
bacteria.
Where do b lymphocytes originate and mature
Originate from stem cells in the bone marrow, and mature in the
spleen and lymph nosed
What is the humoral response?
• Each B lymphocyte has receptors for the detection of its specific antigen
• Activation stimulates the rapid increase of antibody producing cells, plasma cells (produce antibodies), and memory cells
• Memory cells remain in the circulation ready to divide if the same antigen is encountered
again. Turn into plasma cells and release antibodies
Phagocytes role in humoral response
• An antigen-antibody complex means the antigen is inactive, for example the microbes can agglutinate which increases the rate of engulfment by phagocytes in humoral response.
Describe the features of antibodies and their interactions with antibodies
• Antibodies are proteins (globulins) which are specific to the antigen with which they bind
to form an antigen-antibody complex
• Antibodies are Y- shaped, formed from four polypeptide chains and have two binding
sites
Where do T lymphocytes originate and where are they activated?
T lymphocytes, which also originate from stem cells in the bone marrow, but are
activated in the thymus gland
What is the cell-mediated response?
- Detection of the corresponding specific antigen causes the proliferation of T lymphocytes;
- There are many subpopulations of T cells which T lymphocytes can divide to make
What cells are produced during cell-mediated response and what are their role?
1) Effector cells (T killer or cytotoxic T lymphocytes) which cause lysis of the target cells
2) Memory cells which remain dormant until the host is next exposed to the antigens
3) Helper T cells which cooperate with B lymphocytes to initiate an antibody response
4) T cells do this by releasing cytokines which stimulate phagocytic cells, clonal expansion of B and T lymphocytes and cause B lymphocytes to make antibodies
What is the primary immune response?
• Following first exposure to a foreign antigen there is a latent period where macrophages carry out phagocytosis and incorporate foreign antigen into their cell membranes - antigen presentation
• T helper cells detect these antigens and secrete cytokines which stimulate B cells and
macrophages
• B cells are activated and undergo clonal expansion – some then differentiate to become
antibody secreting plasma cells with short lives and others to become long lived memory
cells that retain the ability to undergo mitosis
How long does it take for a primary response to work?
A low level of antibody is secreted which over a period of 2 – 3 weeks clears the infection
and symptoms disappear.
What is a secondary immune response?
• Re-exposure to the same antigen means a very short latent period due to the
presence of memory cells;
• A small amount of antigen is required to stimulate rapid production of plasma cells
• Antibody levels increase 10-100 times greater than the initial response and in a very short time
• Antibody levels stay high for longer and no symptoms develop
