Ch 15 BOOK questions FINAL

A 3-year-old boy with an X-linked defect in the Bruton tyrosine kinase (BTK) gene is impaired in which of the following mechanisms? A. Antibody-mediated bacterial clearance B. Formation of the membrane attack complex C. Delayed (-type) hypersensitivity (DTH) responses D. IFN-')' secretion by CD4 + T cells E. T-cell precursor migration to the thymus

The correct answer is A. Bruton agammaglobulinemia results in a near or total absence of B cells and immunoglobulins; hence antibodymediated responses to microbes are severely impaired. Even in the absence of antibodies and the classical pathway of complement activation, the membrane attack complex can be generated through the MBL and alternative pathways. Antibodies are not involved in the other choices

A 3-month-old male infant has recurrent infections and is found to have an impaired ability to kill microbes by the nitroblue tetrazolium test (which evaluates effectiveness of degradative enzymes). Which of the following conditions is most likely responsible for the findings in this patient? A. Chediak-Higashi syndrome B. Chronic granulomatous disease C. Hereditary angioedema D. HIV/AIDS E. Waldenstrom macroglobulinemia

The correct answer is B. Chronic granulomatous disease is caused by defects in various degradative enzymes or other molecules involved in the oxidative burst. Chediak-Higashi syndrome is caused by an inability to fuse lysosomes with phagosomes. HIV/AIDS results from progressive destruction of CD4 + T cells. Although HIV can infect macrophages and dendritic cells, they remain capable of normal phagolysosome function. Hereditary angioedema results from a deficiency in C1 inhibitor, and Waldenstr6m macroglobulinemia is caused by excessive production of lgM.

A 21-year-old woman has a history since childhood of recurrent episodes of swelling of the submucosal and subcutaneous tissue of the gastrointestinal and respiratory tracts. Her C1 inhibitor level is less than 5% of the reference value. These findings support a diagnosis of A. DiGeorge syndrome. B. hereditary angioedema. C. nutrition-based immune deficiency. D. paroxysmal nocturnal hemoglobinuria. E. Wiskott-Aidrich syndrome.

The correct answer is B. Hereditary angioedema is caused by deficient levels of C1 inhibitor. DiGeorge syndrome is caused by aberrant development of the thymus. Nutrition-based immunodeficiencies are not characteristically identified by severely reduced levels of specific cell types or related molecules. Paroxysmal nocturnal hemoglobinuria is caused by a deficiency of CD59, and Wiskott-Aidrich syndrome is caused by a deficiency of the Wiskott-Aidrich syndrome protein.

A female neonate has a malformed jaw, cardiac abnormalities, and hypocalcemia, in addition to diminished cell-mediated and B-cell responses. Which of the following immune deficiencies should be included in the differential diagnosis of this patient? A. Adenosine deaminase (ADA) deficiency B. DiGeorge syndrome C. Hereditary angioedema D. Severe combine immunodeficiency disease (SCID) E. Wiskott-Aidrich syndrome

The correct answer is B. The defects in jaw and cardiac structure and the defective calcium metabolism (because of abnormal parathyroid development) point to aberrant development of structures derived from the third and fourth pharyngeal pouches. None of the other diseases given are associated with these accompanying features. This individual is likely to also include the thymus, and this patient is likely to have an underdeveloped thymus, which is a hallmark of DiGeorge syndrome

A 6-month-old male infant has diarrhea, extensive fungal infections, and skin rashes and has failed to gain weight. He is deficient in both T- and B-cell function. The thymus is of normal size. The most likely prospect for permanent restoration of normal immunity for this patient would be A. an antibiotic "cocktail" given at regular intervals. B. bone marrow transplantation. C. exogenous immunoglobulins administered periodically. D. isolation to an antiseptic environment. E. thymic hormones given throughout his life

The correct answer is B. The signs suggest a defect in the lymphocytic lineage. This could potentially be permanently alleviated by replacement of defective stem cells through bone marrow transplantation. Isolation is beneficial but is a severe imposition on the quality of life and constitutes protection rather than restoration of function. The remaining choices require constant repetitive application but not permanent restoration of function.

A 5-year-old girl has a small deletion in chromosome 22. She has impaired thymus development with a significant deficiency in the number of functional T cells. The most likely etiology for these findings is A. adenosine deaminase (ADA) deficiency. B. Chediak-Higashi syndrome. C. DiGeorge syndrome. D. hereditary angioedema. E. severe combined immunodeficiency (SCID).

The correct answer is C. Impaired thymic development leading toT-cell dysfunction and small deletions in chromosome 22 are characteristic of DiGeorge syndrome. Thymic development is normal in all of the other choices.

A 24-year-old male presents with fever, cough, and night sweats. Examination reveals an elevated temperature, increased respiratory rate, oral thrush (fungal infection), and decreased breath sounds in the right midlung field. Laboratory testing reveals a CD4 count of 60/ml (reference range: 400/ml). On the basis of these findings, the most likely underlying process is A. autoimmune disease with pneumonia. B. bacterial pneumonia. C. HIV/AIDS with possible mycobacterium tuberculosis. D. hypersensitivity pneumonitis. E. Mycobacterium tuberculosis infection only.

The correct answer is C. The key feature is the extreme deficiency of CD4 + T cells that is characteristic of HIV/AIDS. None of the other choices would be associated with this finding. Respiratory difficulties caused by Mycobacterium tuberculosis infection are frequently seen in HIV/AIDS patients.

A 2-month-old male infant presents with persistent diarrhea, signs and symptoms of Pneumocystis carinii pneumonia, and an oral fungal infection with Candida albicans. His weight is in the 1Oth percentile. Test results for HIV are negative by polymerase chain reaction. The most likely cause of these findings is A. grossly reduced levels of B cells. B. an X-linked inheritance of HLA genes. C. defective isotype switching. D. defective T-cell function. E. selective lgA deficiency

The correct answer is D. The fungal infection is highly suggestive of aT-cell defect. Choices A, C, and E do not of themselves imply a deficiency in T-cell function. HLA genes are autosomal, not X-linked.