Content Summary:
Immunology is the study of the components of the immune system and their function. The human immune system provides a defense against potential pathogens (disease causing microorganisms). This defense can be mounted in one of two ways: 1) innate (nonspecific) immunity and 2) adaptive (specific) immunity. Innate immunity provides resistance to all pathogens because it is an inherited part of each cell's structure. Adaptive immunity provides resistance to specific pathogens. Innate and adaptive immunities can work together, the complement system, and one of these responses is inflammation.

Summary #1
The thymus is a primary lymphoid organ which grows during childhood, atrophies after puberty and is much smaller in adults. It is a soft, bilobed gland located below the thyroid gland and above the heart. The immune system matures after a child reaches 2 years of age, so prior to that, a child is more susceptible to disease and illnesses. Lymphocytes (unspecified cells/stem cells) are formed in the bone marrow during fetal development and in newborns. They are released from the bone marrow, travel to the thymus, mature and become T cells. T cells that are stimulated by pathogenic antigens can live for years. As an adult, reproduction of T cells slows and they are produced in the secondary lymphoid organs.

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Summary #2
Secondary lymphoid organs:
  • spleen
    • filters blood
    • provides lymphocyte production
    • stores RBC and platelets
    • major site where macrophages destroy and remove RBC
  • tonsils\
    • produce lymphocytes
    • find and destroy pathogens
  • lymph nodes
    • filter and cleanse lymph
    • trap damaged cells, cancerous cells and bacteria which are destroyed by macrophages
  • Peyer's patches
    • specialized lymph nodes around the intestines
    • protect areas where antigens could enter
Lymphocytes come from the bone marrow and thymus to these organs, circulate through the blood and lymph where they encounter pathogenic antigens. Antigen presenting cells secrete chemokines that help lymphocytes find their specific antigens.

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Summary #3
Autoimmune diseases are those in which the body does not recognize its own antigens and attacks them. Failure to recognize self-antigens causes autoreactive T cells to activate and autoantibodies are produced by B cells. This response brings inflammation and organ damage. There are over 40 known and/or suspected autoimmune diseases. Some common diseases are: lupus, rheumatoid arthritis, multiple sclerosis, Grave's disease and type I diabetes mellitus. Autoimmune diseases affect more women then men and have no cure. There are many reasons why the body does not recognize its own antigens.

Application:
Immunology was an interesting chapter because it again showed me how our bodies are continually working to protect itself while we are completely unaware. The only time we really know that something is going on is when symptoms such as fever, inflammation, sleepiness, low iron, muscle fatigue and pain occur. Our bodies are so amazing! Learning about the intricacies of immunology made me appreciate all the more the defense our body wages on a daily basis.

As an OTA, my patients may suffer with autoimmune diseases and I will need to know how their symptoms affect their ADL. Daily issues of muscle fatigue and pain will need to be addressed. I will also need to be aware of any symptoms of inflammatory response.

Studying this chapter has helped me understand what may be happening to friends and family who suffer from autoimmune diseases. I know someone who suffers with each of the diseases mentioned in summary #3, and even though only 5% to 7% of our population has an autoimmune disease, it seems much more common. This is just another reason for me to stay aware of the workings of our immune system.

Essential Questions:
Comparisons and contrasts to the following categories are included below:
  • active immunity vs passive immunity
    • active immunity (AI)- requires prior exposure to the specific antigen, either from the person's antibodies or from vaccination
      • naturally acquired active immunity results from contraction of a disease, then recovery
      • artificially acquired active immunity results from a vaccination
    • passive immunity (PI)-requires the transfer of antibodies to a recipient from a human or animal donor
      • naturally acquired passive immunity results from maternal antibodies received, such as a newborn
      • artificially acquired passive immunity results from injections of antibodies (immunoglobulins)
    • AI and PI are different in how they are acquired
    • AI and PI are similar in that they both provide immune defense
  • innate immunity vs adaptive immunity
    • innate (nonspecific, II) immunity-defense mechanisms are part of the structure within each organism
    • adaptive (specific, AI) immunity-produced by genetic changes within lymphocytes due to exposure to specific pathogens
    • II and AI are different because of their development, II is always present and AI develops after exposure to the pathogen
    • II and AI are similar in that they both provide immune defense
  • cell-mediated immunity vs humoral immunity
    • cell-medicated immunity (CMI)-T lymphocytes directly attack and destroy foreign and intracellular pathogens
      • T lymphocytes do not secrete antibodies, they must come into close proximity of the host cell
    • humoral immunity (HI)-B lymphocytes secret antibodies into the blood and lymph
      • B lymphocytes combat bacterial and some viral infections
    • CMII and HI are different because ones cells secrete antibodies, and the other does not
    • CMI and HI are similar in that they both provide immune defense

The process of an inflammatory response starts when complement proteins are activated by B lymphocytes during a humoral response. Antigens on B lymphocytes bind to antibodies and coat the bacteria. The complement is activated, neutrophils and macrophages begin phagocytosis, and mast cells release histamine and other chemicals that promote capillary permeability and extraversion of leukocytes that invade the site, causing inflammation. Symptoms that occur at the site of inflammation are: redness, warmth, swelling, pus and pain. Inflammatory responses serve to protect the body, but sometimes they can cause damage to tissues.

References: Human Physiology by Stuart Ira Fox, Anatomy and Physiology by Stanley E Gunstream, andTaber's Cyclopedic Medical Dictionary