Abbas chapter 1 Flashcards
What are the principle components of the innate immune system?
1) Physical & chemical barriers (e.g epithelia, anti-microbial chemicals produced at epithelial surfaces).
2) Phagocytic cells (i.e neutrophils & macrophages).
3) Blood proteins; including complement system & other mediators of inflammation.
4) Cytokines; which regulate & coordinate many activities of cells of innate immunity.
Define antigens (modern)
Substances that bind to specific lymphocyte receptors,
whether or not they stimulate immune responses.
What are the two types of adaptive immune responses
Humoral & cell mediated immunity.
What is humoral immunity mediated by?
Antibodies in the blood & mucosal secretions.
What cells involved in humoral immunity produce antibodies?
B lymphocytes (B cells).
How do antibodies work?
They recognise microbial antigens, neutralise the infectivitity & target microbes for elimination by various effector mechanisms (e.g phagocytosis).
How are antibodies transported into the lumen of mucosal organs & through the placenta?
Active transport.
What cells mediate cell mediated immunity?
T-lymphocytes (T-cells).
What is active immunity?
Immunity that is induced by exposure to a foreign antigen.
What is passive immunity? Give an example.
Process where by the patient becomes immune to the particular antigen without ever being exposed due to receiving serum or lymphocytes from an exposed/immunised individual e.g tetanus antitoxin or anti-venom for snake bites or transfer of maternal antibodies.
What are immunogens?
Substances that stimulate immune responses.
What is opsonization?
Coating of pathogens with antibodies in order to increase their susceptibility to ingestion by phagocytes
What parts of an antigen are specifically recognised by individual lymphocytes?
The determinants or epitopes.
What does the lymphocyte repertoire refer to?
The total number of antigenic specificities of the
lymphocytes in an individual.
What are the cardinal features of the adaptive immune system?
1) Specificity.
2) Diversity.
3) Memory.
4) Clonal expansion.
5) Specialisation.
6) Contraction & homeostasis.
7) Non-reactivity to self.
What is clonal expansion? How is it beneficial?
An increase in the number of cells that express identical
receptors for the antigen.
Helps to fight off rapidly dividing pathogens.
What is the benefit of immunological memory? Give specific examples.
Enhanced ability to respond again to the antigen; second & subsequent exposures are often more rapid, larger & qualitatively different from the 1st or primary immune response to the antigen. E.g Memory B cells produce antibodies that bind antigens with higher affinities on repeat exposure. Memory T cells react much quicker and more vigorously to antigen challenge vs naive T-cells.
How do non-memory lymphocytes die after an immune response?
Apoptosis.
What is immunological unresponsiveness also called?
Tolerance.
What type of B lymphocyte secretes antibodies?
Plasma cells.
Can T lymphocytes respond to soluble antigens? Why/ why not.
No. T cells recognise peptides derived from foreign proteins that are bound to host proteins (major histocompatibility complex molecules) which are expressed on surfaces of other cells.
What do helper T-cells secrete? How does this help?
Cytokines.
Stimulates the proliferation & differentiation of T-cells, activate other cells including B cells, macrophages & other leukocytes.
What are cytokines?
Messenger molecules of the immune system.
How do cytotoxic T-lymphocytes work?
Kill cells containing foreign antigens (i.e viruses or intracellular pathogens).
Name 3 classes of lymphocytes.
1) B cells.
2) T cells.
3) Natural killer cells.
How can classes of lymphocytes be distinguished?
By expression of surface proteins called CD molecules (numbered).
What is the role of antigen-presenting cells?
To capture & present an antigen to specific lymphocytes.
What are the most specialised APCs?
Dendritic cells.
Give some examples of effector cells.
Activated T cells, mononuclear phagocytes & other leucocytes.
Why is cytokine synthesis transient?
Synthesis is initiated by new gene transcription as a result of cellular activation, the transcriptional activation is transient & the messenger RNAs encoding most cytokines are unstable & often rapidly degraded.
Do cytokines have?
1) Autocrine function (act on the cell that they are produced by).
2) Paracrine function (act on a near by cell).
3) Endocrine function (act at a site distant to production).
All three.
What role does IL-2 have in the immune response?
IL-2 is a growth factor that acts on the antigen-activated lymphocytes and stimulates their proliferation (clonal expansion)
What is IL-2 produced by?
CD4+ helper T cells
