Page 132 - Alaska A & P Primer

diseases is, more often than not, unknown, and the treatments are usually based on resolv- ing the symptoms using immunosuppressive and anti-inflammatory drugs such as ster- oids. These diseases can be localized and crippling, as in rheumatoid arthritis, or diffuse in the body with multiple symptoms that differ in different individuals, as is the case with systemic lupus erythematosus.
Autoimmune Disorders: Rheumatoid Arthritis and Lupus (a) Extensive damage to the right hand of a rheumatoid arthritis sufferer is shown in the x-ray. (b) The diagram shows a variety of possible symptoms of systemic lupus erythematosus.
Environmental triggers seem to play large roles in autoimmune responses. One explana- tion for the breakdown of tolerance is that, after certain bacterial infections, an immune response to a component of the bacterium cross-reacts with a self-antigen. This mecha- nism is seen in rheumatic fever, a result of infection with Streptococcus bacteria, which causes strep throat. The antibodies to this pathogen’s M protein cross-react with an anti- genic component of heart myosin, a major contractile protein of the heart that is critical to its normal function. Overall, there are more than 80 different autoimmune diseases, which are a significant health problem in the elderly.
21.7 Transplantation and Cancer Immunology
The immune responses to transplanted organs and to cancer cells are both important medi- cal issues. With the use of tissue typing and anti-rejection drugs, transplantation of organs and the control of the anti-transplant immune response have made huge strides in the
past 50 years. Although it is clear that the immune system can recognize some cancers
and control them, others seem to be resistant to immune mechanisms.
It is clear that with some cancers, for example Kaposi’s sarcoma, a healthy immune system does a good job at controlling them. This disease, which is caused by the human herpesvi- rus, is almost never observed in individuals with
strong immune systems, such as the young and
immunocompetent. Other examples of cancers caused by viruses include liver cancer caused by the hepatitis B virus and cervical cancer caused by the human papilloma virus. As these last two vi- ruses have vaccines available for them, getting vaccinated can help prevent these two types of cancer by stimulating the immune response.
21.7 OBJECTIVES
1. Show how the immune response is able to control some cancers and how this immune response might be enhanced by cancer vaccines
Karposi’s Sarcoma Lesions (credit: National Cancer Institute)
On the other hand, as cancer cells
are often able to divide and mutate
rapidly, they may escape the immune response, just as certain pathogens such as HIV do. There are three stages in the immune response to many cancers: elimination, equilibrium, and escape. Elimination occurs when the immune response first develops toward tumor- specific antigens specific to the cancer and actively kills most cancer cells, followed by a period of controlled equilibrium during which the remaining cancer cells are held in check. Unfortunately, many cancers mutate, so they no longer express any specific antigens for the immune system to respond to, and a subpopulation of cancer cells escapes the immune response, continuing the disease process.
This content is available for free at https://cnx.org/content/col11496/1.7
State of Alaska EMS Education Primer - 2016
131
It is tempting to focus on the complexity of the immune system and the problems it causes as a negative. The upside to immunity, however, is so much greater: The benefit of staying alive far outweighs the negatives caused when the system does sometimes go awry. Work- ing on “autopilot,” the immune system helps to maintain your health and kill pathogens. The only time you really miss the immune response is when it is not being effective and illness results, or, as in the extreme case of HIV disease, the immune system is gone com- pletely.