A 64-year-old man undergoes surgery to excise 18 inches of bowel with adenocarcinoma. When the tissue and draining mesenteric lymph nodes are sent for pathologist’s examination, the Peyer patches are noted to be hyperplastic with IgA-secreting plasma cells, but there is no secretory IgA found in the lumen of the colon. Which of the following changes in the bowel epithelium could explain this finding?( )
A. Failure of isotype switching
B. Failure of variable domain gene-segment rearrangement
C. Loss of J chain synthesis
D. Loss of the polyimmunoglobulin receptor
E. Loss of Th2 cells
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A 26-year-old obstetric patient becomes ill during the first trimester of pregnancy with fever and lymphadenopathy. She is found to have a rising titer of anti-Toxoplasma gondii antibodies. She delivers a full-term baby with no apparent signs of in utero infection. The best test to diagnose acute infection in the neonate would be a parasite-specific ELISA for which isotype of immunoglobulin?( )
A. IgA
B. IgD
C. IgE
D. IgG
E. IgM
It has been learned in several experimental systems that proliferation and differentiation of T lymphocytes in response to tumor cells is low because tumor cells lack the necessary costimulatory molecules for lymphocyte activation. If melanoma cells from a patient were induced to express these costimulatory molecules by transfection, production of an effective antitumor response might occur. Which of the following molecules would be the best candidate for transfection of tumor cells to achieve this end?( )
A. B7
B. CD2
CD4
D. CD28
E. LFA-1
A radioactive tracer dye is injected subcutaneously into the forearm of an experimental subject. What is the first area of the first draining lymph node that would develop significant radioactivity?( )
A. Cortex
B. Medulla
C. Paracortex
D. Primary follicle
E. Subcapsular sinus
An 18-year-old member of a college soccer team is seen by a physician because of chest tightness and dyspnea on exertion. A 15-cm mediastinal mass is detected radiographically. Eighty percent of the white blood cells in the peripheral blood are small, abnormal lymphocytes with lobulated nuclei and scant cytoplasm. Immunophenotyping of the abnormal cells shows them to be CD4+ and CD8+. Where would such cells normally be found in the body?( )
A. Bone marrow
B. Peripheral blood
C. Thymic cortex
D. Thymic medulla
E. Splenic periarteriolar lymphoid sheaths