Which intrinsic factor of the innate immune system provides protection against the invasion of microorganisms?

• A. Production of antibodies by B cells
• B. Clonal expansion of lymphocytes
• C. Lysozyme present in mucosal secretions
• D. Activation of memory T cells

Answer: (C)

Verified step by step guidance

1. Understand that the innate immune system provides the first line of defense against pathogens and includes physical, chemical, and cellular barriers that act immediately or within hours of an antigen's appearance in the body.
2. Recognize that production of antibodies by B cells and clonal expansion of lymphocytes are part of the adaptive immune system, which is specific and develops over time after exposure to a pathogen.
3. Recall that memory T cells are also components of the adaptive immune system, responsible for faster responses upon re-exposure to a pathogen.
4. Identify that lysozyme is an enzyme found in mucosal secretions such as saliva, tears, and mucus, which acts as an intrinsic chemical factor of the innate immune system by breaking down bacterial cell walls, thus providing protection against microbial invasion.
5. Conclude that among the options, lysozyme present in mucosal secretions is the intrinsic factor of the innate immune system that provides immediate protection against microorganisms.