In sickle cell disease, substitution of which amino acid at the sixth position of the beta-globin chain produces HbS?
1) Glutamic acid replaced by valine
2) Valine replaced by glutamic acid
3) Lysine replaced by asparagine
4) Glycine replaced by alanine

Which finding is most characteristic of chronic (as opposed to acute) viral hepatitis on biopsy?
1) Ballooning degeneration of hepatocytes
2) Canalicular bile plugs
3) Portal fibrosis with formation of bridging fibrous septa
4) Isolated hepatocyte necrosis

Transfusion-transmitted infections that must be routinely screened for prior to blood transfusion include all of the following EXCEPT:
1) HIV
2) Hepatitis B and C
3) Syphilis
4) Rabies

Which selectin, expressed on endothelial cells, is considered a hallmark of acute cytokine-mediated inflammation and binds sialyl-Lewis X on leukocytes?
1) L-selectin
2) P-selectin
3) E-selectin
4) N-selectin

Which cells are considered the most important source of histamine and are key effectors in immediate (type I) hypersensitivity?
1) Eosinophils
2) Mast cells and basophils
3) Neutrophils
4) Plasma cells