Final answer:
Defensins are least likely to be found in significant levels in the liver. They are part of the innate immune defense, associated with areas in direct contact with the external environment such as the skin, lungs, intestine, and bladder.
Step-by-step explanation:
You would be least likely to find significant levels of defensins in the liver (Option C). Defensins are small antimicrobial peptides that contribute to the innate immune response by destroying the cell membrane of bacteria and other pathogens. They are part of the first line of defense and are most often associated with barriers such as the skin and mucosal surfaces. Considering the locations provided, the skin, lungs, intestine, and bladder are all areas where defensins can be prominent due to their role in directly defending against external pathogens that may try to enter the body. The liver, while also an important organ in the immune system, does not have that direct contact with the external environment, and therefore it generally has lower levels of defensins compared to other listed sites.