CAS PS 332 Lecture Notes - Lecture 16: Innate Immune System, Antigen, Cytokine

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Published on 6 Apr 2020
Professor
April 2nd, 2020
Lecture 16
Immune mediated illness
Objectives:
- Explain the main findings from the “Pittsburgh cold studies”
o Experimental paradigms used
o Role of stress and social support
o Proposed physiological pathway
- Identify the main findings of research linking stress and wound healing
- Explain how HIV affects immune functioning
- Distinguish HIV and AIDS
o Explain what happens during the three stages of HIV progression
- Identify the 7 steps in the HIV life cycle
- Identify the primary routes of HIV transmission (routes of infection)
The immune system: a brief review
Function and levels:
Two main functions:
- Protect body from invasion by antigens
o Bacteria, viruses, fungi
- Remove damaged or mutant cells
o E.g. cancer cells
Three levels:
- Physical barriers
o E.g. skin, mucosal tracts of airway and gut
- Innate immune system (nonspecific)
o General, fast, non-specific response
- Acquired immune system (specific)
o Developed much later to fight viruses only
o Slower, specific response to one antigen
Innate immune system:
- Macrophage: “defender” cell that is programmed to recognize common antigens
o Attracted to chemicals released by antigen
o Travels to side of antigen
o Reaches out and “grabs” antigen phagocytosis
Literally means “big eater”
- Cytokines: hormone-like messengers that facilitate communication among immune cells
o Coordinate inflammatory response
Signal to immune cells that there is an invader
Other immune cells exit the blood vessels near antigen to restore
damaged tissue
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Local and systemic effects
- E.g. interleukin 6 (IL-6): secreted by T-cells and macrophages
Acquired immune system:
- Primary cell types: B- and T- cells
o B-cells: white blood cells that attack antigens by producing specific antibodies
B-cells make antibodies (aka that protect the body against specific
antigens)
B-cell senses cognate antigen proliferation
o Plasma vs memory cells
o Clones reduce antibodies specific to cognate antigen
o Antibodies “tag” antigens for destruction
Primary vs secondary responses
Primary response is slower and smaller than the secondary
response because the primary response is the first that that we
encounter the antigen
Memory cells know what to do when we encounter that antigen
in the future and proliferate the response
o T-cells: white blood cells that attack antigens directly, without producing
antibodies
Lymphocytes that respond to specific cognate antigens and proliferate
Cytotoxic T-cells: kill virus-infected cells
o Bind to infected cells and inject lethal toxin infected cell
dies
T-helper cells: direct the action of the immune response by
secreting cytokines stimulate additional immune cells
o B-cells, cytotoxic T-cells, macrophages
T-suppressor cells: produce chemicals that downregulate immune
responding and alert T and B cells when an antigen is vanquished
Cohen Article (2005): the Pittsburgh Cold Studies
Goal of exercise:
- Identify physiological pathways through which stress and social support may change
your risk of developing a respiratory cold
o Distinguish different effects of various types of stressors and social support
Class discussion
1. What is the goal of this line of research? It is a really innovative idea: the idea that about
20 years ago, this research group out of Pittsburgh wanted to figure out the
hypothetical connection between stress and illness (specifically infectious illness). There
are epidemiological findings and descriptive studies that linked this, but no
experimental designs in human to conclude the findings. How can we make it an
experimental design? They recruited people to spend 8 days in a hotel. They enrolled
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