Final answer:
The useful plasma component for immunodeficient individuals without antibodies is serum. Serum contains antibodies that provide defense against viruses and bacteria.
Step-by-step explanation:
The plasma component that would be useful in immunodeficient individuals without antibodies is serum. Serum is the plasma component of blood without the coagulation factors, and it contains antibodies, which are specialized proteins that are important for defense against viruses and bacteria. It also transports lipids, nutrients, hormones, and other substances. By receiving donated serum, immunodeficient individuals can gain temporary passive immunity through the presence of antibodies.