Answer to Question 1
ANS: A, B, C
Directly, antibodies can affect infectious agents or their toxic products by neutralization (inacti-vating or blocking the binding of antigen to receptors), agglutination (clumping insoluble particles that are in suspension), or precipitation (making a soluble antigen into an insoluble precipitate). Indirectly, antibodies activate components of innate resistance, including complement and phag-ocytes. Antibodies are generally a mixed population of classes, specificities, and capacity to pro-vide the functions listed above.
Answer to Question 2
ANS: D
The amount of antibody in a serum sample is referred to as the titer; a higher titer indicates more antibodies. Culture determines the type of organism that causes an infection, and sensitivity identifies the antibody it is sensitive to. The terms agglutination and precipitation are not used to identify a test to determine immunity.