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Ch. 13 - Immune System Disorders
Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition
Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook
Chapter 13, Problem 3

Indicate the true statements, and then reword the false statements so they are true.
a. Immunodeficiencies are associated with a decreased cancer risk
b. Type I reactions are mediated by IgG antibodies
c. Autoimmune disorders are not caused by type I hypersensitivities
d. Systemic lupus is mainly mediated by a type III hypersensitivity
e. A person with type 0- blood is called a universal donor
f. Immunotherapies are useful to reduce type II reactions

Verified step by step guidance
1
Step 1: Analyze statement (a): 'Immunodeficiencies are associated with a decreased cancer risk.' Consider the role of the immune system in surveilling and eliminating cancer cells. Immunodeficiencies typically impair this surveillance, which can increase cancer risk. Therefore, this statement is false. Reword it to: 'Immunodeficiencies are associated with an increased cancer risk.'
Step 2: Analyze statement (b): 'Type I reactions are mediated by IgG antibodies.' Recall that Type I hypersensitivity reactions are immediate allergic reactions mediated by IgE antibodies binding to mast cells and basophils. Since IgG is not involved in Type I reactions, this statement is false. Reword it to: 'Type I reactions are mediated by IgE antibodies.'
Step 3: Analyze statement (c): 'Autoimmune disorders are not caused by type I hypersensitivities.' Understand that autoimmune disorders are generally caused by other types of hypersensitivities (types II, III, or IV), not Type I. This statement is true as is.
Step 4: Analyze statement (d): 'Systemic lupus is mainly mediated by a type III hypersensitivity.' Recognize that systemic lupus erythematosus (SLE) involves immune complex deposition, characteristic of Type III hypersensitivity. This statement is true as is.
Step 5: Analyze statement (e): 'A person with type 0- blood is called a universal donor.' Recall that type O negative blood lacks A, B, and Rh antigens, making it compatible for transfusion to most recipients. This statement is true as is. Then analyze statement (f): 'Immunotherapies are useful to reduce type II reactions.' Consider that immunotherapies can modulate immune responses, including those involved in Type II hypersensitivities (antibody-mediated cytotoxic reactions). This statement is true as is.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Immunodeficiencies and Cancer Risk

Immunodeficiencies weaken the immune system, reducing its ability to detect and destroy cancerous cells, which actually increases cancer risk. A healthy immune system plays a key role in tumor surveillance by identifying and eliminating abnormal cells before they develop into cancer.
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Types of Hypersensitivity Reactions

Hypersensitivity reactions are immune responses that cause tissue damage. Type I reactions are immediate and mediated by IgE antibodies, not IgG. Type II involves IgG or IgM antibodies targeting cells, Type III involves immune complexes, and Type IV is cell-mediated.
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Blood Groups and Universal Donors

Blood group O-negative individuals are called universal donors because their red blood cells lack A, B, and Rh antigens, minimizing the risk of immune reactions in recipients. This makes O-negative blood compatible with most recipients in transfusions.
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