÷ÈÓ°Ö±²¥

Which of the following is not a surface barrier to infection? a. skin b. acidic gastric fluid c. lysozyme in saliva d. resident bacterial populations e. complement activation f. flushing action of diarrhea

________are targets of cytotoxic T cells. a. Extracellular virus particles in blood b. Virus-infected body cells or tumor cells c. Parasitic worms in the liver d. Bacterial cells in pus e. Pollen grains in nasal mucus