Porth's Essentials of Pathophysiology, 4e

372

Infection and Immunity

U N I T 4

R E V I EW E X E R C I S E S 1. A 32-year-old man presents in the allergy clinic with complaints of allergic rhinitis or hay fever. His major complaints are those of nasal pruritus (itching), nasal congestion with profuse watery drainage, sneezing, and eye irritation. The physical examination reveals edematous and inflamed nasal mucosa and redness of the ocular conjunctiva. He relates that this happens every fall during “ragweed season.” A. Explain the immunologic mechanisms that are responsible for this man’s symptoms. B. What type of diagnostic test might be used? C. What type(s) of treatment might be used to relieve his symptoms? 2. Persons with intestinal parasites and those with allergies may both have elevated levels of eosinophils in their blood. A. Explain. 3. A 20-year-old woman has been diagnosed with IgA deficiency. She has been plagued with frequent bouts of bronchitis and sinus infections. A. Why are these types of infections particularly prominent in persons with an IgA deficiency? B. She has been told that she needs to be aware that she could have a severe reaction when given unwashed blood transfusions. Explain. 4. Persons with impaired cellular immunity may not respond to the tuberculin test, even when infected with Mycobacterium tuberculosis. A. Explain. 5. A 29-year-old woman presents to the clinic for her initial obstetric visit about 10 weeks into her pregnancy. A. This woman is in a monogamous relationship. Should an HIV test be a part of her initial blood work? Why? B. The woman’s HIV test comes back positive. What should be done to decrease the risk of transmitting HIV to her child? C. The infant is born, and its initial antibody test is positive. Does this mean the infant is infected? How is the diagnosis of HIV infection in a child younger than 18 months made, and why is this different than the diagnosis for adults? 6. A 40-year-old man presents to the clinic very short of breath, and after a radiograph and an examination, he is diagnosed with PCP. His provider does an HIV test, which is positive. Upon further testing, the man’s CD4 + cell count is found to be 100 cells/ μ L and his viral load is 250,000 copies/mL.

SUMMARY CONCEPTS

■■ Immunodeficiency is an absolute or partial loss of the normal immune response, which places a person at increased risk for development of infections or malignant complications. It can be classified as primary (i.e., congenital or inherited) or secondary (i.e., due to another disease or condition). ■■ Immunodeficiency can affect the humoral or cellular components of the adaptive immune system. Defects in humoral immunity increase the risk of recurrent pyogenic infections but have less effect on the defense against intracellular bacteria (mycobacteria), fungi, protozoa, and viruses (except for the enteroviruses that cause gastrointestinal infections). Defects in cellular immunity increase the risk of developing fungal, protozoan, viral, and intracellular bacterial infections, and malignant cell proliferation. ■■ Acquired immunodeficiency syndrome (AIDS), the most common type of secondary immunodeficiency, is caused by infection with the human immunodeficiency virus (HIV), a retrovirus that infects the body’s CD4 + T cells and macrophages. Destruction of CD4 + cells constitutes an attack on the entire immune system because this subset of lymphocytes exerts critical regulatory and effector functions that involve both humoral and cellular immunity. ■■ The clinical course of HIV infection can be divided into three phases: a primary phase that occurs shortly after infection and is usually manifested by mononucleosis-like symptoms, a latency phase that may last for years, and an overt AIDS phase that is characterized by a marked decrease in CD4 + T cells and the development of opportunistic infections, malignancies, wasting syndrome, and metabolic disorders.There is no cure for AIDS.Treatment largely involves the use of drugs that interrupt the replication of HIV and prevention or treatment of complications such as opportunistic infections. ■■ Women who are infected with HIV may transmit the virus to their offspring in utero, during labor and delivery, or through breast milk. Diagnosis of HIV infection in children born to HIV-infected mothers is complicated by the presence of maternal HIV antibody, which crosses the placenta to the fetus. This antibody usually disappears within 18 months in uninfected children.