ASEN 5016 Lecture 14b: Immune
System
OBJECTIVES
The
Immune System
Cell recognition: self vs. non-self
Substance recognition:
-Antigens
-Antibodies
-Epitopes
Innate Immunity
-Born
with it.
-Physical
barriers: skin, mucous membranes
-Protective chemicals:
acid pH, surface lipids
-Enzymes: saliva, digestive
tract enzymes
-Macrophages and
complement
Acquired Immunity
-Antigen
specific
-Memory
-Regulation
Cells of the immune system
T-cells:
-Helper T-cells (CD4+)
-Cytotoxic killer cells
(CD8+)
-Natural killer cells
(NK or CD8+)
B-cells:
- Plasma cells
- Antibody production
Macrophages: T-cell and B-cell stimulation
The Organs of the Immune System
The Bone Marrow:
-Spongy tissue found in
the center of most large bones
-All cells in the IS
initially derive from it
-Produces RBCs and platelets
-Stem cells, reside
within the BM (unspecialized cells)
-Most radiation
sensitive tissue of the human body
Thymus:
-BM T-cell maturation
-Release of mature T-cells into bloodstream
Spleen:
-Immunological filter of
the blood.
-Antigens are brought by macrophages or the
blood itself. B and T-cells are
activated.
-Old RBCs are destroyed.
Lymph nodes (Lymphatic system):
-Immunological filters
of the body fluid called lymph.
-Lymph is drained from
most of our tissues.
-Antigens are filtered
before returning to circulation.
2.
Space
flight-related factors affecting immunity
Factors that can influence physiologic functions
- Launch / Landing
- Microgravity-related effects
- Isolated Confined Environment
- Radiation
- Microbial contamination
- Sleep
disruption
- Nutrition
Other Stressors
-Pre-flight physical training
-Discomfort of lift-off and landing
-Heavy in-flight work and exercise schedules
-Forced adaptation to the confined environment
of the spacecraft
Weightlessness?
Cephalic fluid shift
-Affects lymphatic
system (lymph nodes)
Loss of body fluid
affects plasma protein concentration and osmolality
Bone loss?
Diet
-Recommended
Daily Allowance (RDA)
-Nutrition / SMS
Circadian rhythm and sleep patterns
Radiation?
Stress?
Other effects?
Radiation
-Long
term exposure
-Low
dose effects
-Effects
on bone marrow
Exercise
-Moderate exercise
enhances immune activity
-An increased load can lead
to depression in certain immune responses
-Apollo
and Skylab analyses
Analogous environments on Earth
-Submarines
-Polar stations
-Oil platforms
Growing levels of immune-related problems on
Earth
Increasing
incidence of allergies and auto-immune diseases
Leading
theory is the ‘hygiene hypothesis’
STS-107 experiments
Impairment
of system’s ability to fight infections
Stress-related
reactivation of latent viruses
Observed changes
-Reduction in T-cell counts (cell-mediated
immunity)
-Natural killer cells:
decrease in functionality and concentration.
-Constant immunoglobulin levels (antibodies)
-Immune cells mediators: Interleukin-2
decreases.
Collecting immunological data
in flight is difficult…
Additional
Info (pdf document, see page 12-13) on the effects of space flight on the
immune system, and some other interesting articles in this issue as well
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