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Unit 3 Study Guide: Chapter 13

Terms in this set (21)

Immunodeficiency is the lack of a properly functioning immune system.

Primary immunodeficiency is congenital; the result of a genetic defect; an inborn error that affects one or more immune factors and leads to deficient immunity. There are over 150 lifelong disorders, they are relatively rare and have a broad spectrum of effects (some are manageable and survivable, others have limited treatment options and result in a decreased life span). Patients tend to experience recurring, persistent, and sever infections, often caused by opportunistic pathogens. 50% are due to B cell issues, 30% are linked to T cell defects, 18% are errors in phagocytes, and 2% relate to complement deficiencies. Therapies for primary immunodeficiencies include bone marrow transplants, intravenous or subcutaneous antibody administration, cytokine therapies, and experimental treatments (e.g., stem cell transplants, thymus transplantation, gene therapy).

Secondary immunodeficiencies are acquired (not inborn) and more common than primary immunodeficiencies. In secondary immunodeficiencies, the patient starts out with a normal immune system and then experiences a decline in immune system rigor, often due to age, certain infectious agents (pathogens with virulence factors that directly inhibit host immune defenses by breaking down antibodies, interfering with cellular signaling, or directly infecting immune system cells like HIV which progresses into AIDs when enough helper T cells are lost; examples include Human T cell lymphotropic viruses, Epstein-Barr virus, and Measles virus), medical interventions (chemotherapy, radiation, steroid anti-inflammatory drugs like corticosteroids, anti-seizure medications, and immunosuppressants), and systemic disorders (e.g., diabetes, malnutrition, alcoholism, hepatitis). Secondary immunodeficiencies caused by medical intervention is usually reduced when the patient stops taking the drug, but some patients are not able to stop (organ transplant recipients).
An allergen is any antigen that triggers IgE production; antigens that do not noticeably affect nonallergic individuals. The allergen exposure called sensitizing exposure triggers the immune system to produce IgE. Plasma cells (activated B cells) release IgE which binds to the surface of mast cells or basophils (granulated leukocytes). In post-sensitization exposure, previously made IgE anchors to mast cells, the allergen binds to IgE antibodies, and induces degranulation causing the release of proinflammatory factors, triggering an allergic response.
The signs, symptoms, and severity are affected by the route of exposure and level of IgE produced. Inhaled allergens will cause respiratory issue like coughing or swollen airways; ingested allergens can cause digestive distress, skin manifestation like hives, and respiratory distress. Portals of entry include inhalants, injectants, ingestants, and contactants. Injected allergens like bee stings can allow the allergen to enter the circulatory system which may provoke more severe reactions. The level of IgE produced also affects severity. The spectrum of inflammatory cytokines released by mast cells is directly related to signs and symptoms.
-Prostaglandins can dilate blood vessel, constrict bronchioles, and cause headaches.
-leukotrienes can constrict bronchioles, which can be deadly especially when combined with airway obstruction by mucus buildup. Leukotrienes are released in allergic asthmatic reactions.
-histamine, serotonin, and bradykinin can cause dilated blood vessels and skin manifestations, increased peristalsis of intestine causing diarrhea or vomiting, and/or promoting secretory glands on epithelial tissues, causing runny or stuffed noses.
Examples of autoimmune type IV hypersensitivities:
-Guillain-Barre syndrome: nervous system disorder where T cells attack nerves that regulate muscle contractions; results in loss of motor function or paralysis.
-Hashimoto thyroiditis: T cell-mediated attacks on thyroid resulting in hypothyroidism
-Type I diabetes: insulin-producing cells in the pancreas are destroyed resulting in loss of blood sugar regulation
-Multiple sclerosis: myelin-producing cells are damaged; leads to compromised nerve signaling
-Celiac disease: gluten consumption exposure causes T cells to attack the lining of the small intestine; leads to extreme inflammation and tissue damage; prevents absorption of essential vitamins and minerals from food

Examples of nonautoimmune type IV hypersensitivities (most triggered by haptens):
-Tuberculin skin test: detects exposure to Mycobacterium tuberculosis; tuberculin purified protein derivative (PPD) is injected into the skin of the forearm; injection site is observed within 48-72 hours; positive result recorded if induration develops and lesion meets a certain size criterion
-contact dermatitis: caused by drugs, nickel, chromate, poison ivy toxin (pentadecacatechol); T cells are sensitized (requires a sensitizing and provocative dose); secondary exposure of same antigen leads to inflammation and generates and extremely itchy (pruritic) red rash
-transplant rejection: when donor tissue displays surface molecules of a different MHC class, the T cells of the recipient will recognize its foreignness and react against it
-graft-versus-host disease (GVHD): may occur in bone marrow transplants; where graft attacks host tissues; white blood cells made in the transplanted bone marrow attack the new body they inhibit.