Immune system disorders

Define the terms autoimmune disease, immunodeficiency, and hypersensitivity

Autoimmune disease is when the immune system attacks the body’s own cells. Immunodeficiency is when the immune system is weakened or missing parts, leading to increased infections. Hypersensitivity is an inappropriate or exaggerated immune response that can cause tissue damage. – localized: restricted to a given tissue. – systemic: affects multiple tissues and organ systems

Describe the different subunits of an antibody

An antibody is made of two heavy chains and two light chains. The tips (Fab region) are the antigen-binding sites, while the stem (Fc region) interacts with immune cells and complement proteins.

Define “class switching”

Class switching is when a B cell changes the type of antibody it produces (from IgM/IgD to IgG, IgA, or IgE) depending on the infection, while still recognizing the same antigen.

Explain how it is possible for lymphocytes to attack “self” cells

Lymphocytes can attack self cells if self-tolerance fails during maturation, meaning self-reactive cells are not eliminated, leading to autoimmune disease.

Provide examples of immunodeficiencies. Pick your “favorite” immunodeficiency and describe the cause, signs and symptoms, and possible therapy if any.

Examples include SCID, HIV, and DiGeorge syndrome. Example: HIV is caused by a virus that destroys CD4 T cells, weakening the immune system. Symptoms include frequent infections and progression to AIDS. Treatment includes antiretroviral therapy (ART) to control the virus.

Provide examples of autoimmune diseases. Pick your “favorite” autoimmune disease and describe the organ(s) involved, the mechanism, and possible therapy, if any.

Examples include lupus, type 1 diabetes, and multiple sclerosis. Example: Type 1 diabetes affects the pancreas; the immune system destroys insulin-producing beta cells. This leads to high blood sugar. high blood sugar (hyperglycemia) can weaken the immune response, making individuals more susceptible to infections, slowing wound healing, and increasing the risk of serious illness from viruses and bacteria. treatment includes insulin therapy.

Explain the "hygiene hypothesis.”

The hygiene hypothesis suggests that overly clean environments and antibiotic use reduce exposure to microbes, leading to less immune system training and increased allergies and autoimmune diseases

Describe the four basic hypersensitivities and provide examples of each

Type I: allergies (e.g., anaphylaxis, asthma) driven by IgE and mast cells. Type II: cytotoxic reactions (e.g., hemolytic disease of newborn) involving IgG/IgM against cells. Type III: immune complex reactions (e.g., lupus) involving antigen-antibody complexes. Type IV: delayed hypersensitivity (e.g., contact dermatitis, multiple sclerosis) mediated by T cells :contentReference[oaicite:1]{index=1}

Choose four different hypersensitivities (one of each type) and describe them in detail.

Type I: Anaphylaxis—IgE-mediated rapid allergic reaction causing histamine release and systemic symptoms. Type II: Hemolytic disease of newborn—antibodies attack fetal red blood cells causing anemia. Type III: Lupus—immune complexes deposit in tissues causing inflammation and damage. Type IV: Contact dermatitis—T cells cause delayed skin inflammation after exposure (e.g., poison ivy)