The First and Second Lines of Defense Against Microbial Invasion

Question

The first and second lines of defense against microbial invasion are part of
A) innate immunity.
B) adaptive immunity.
C) species resistance.
D) microbial antagonism.
E) both species resistance and adaptive immunity.

Accepted Answer

The first and second lines of defense, such as physical barriers (e.g. skin, mucous membranes), phagocytic cells (e.g. neutrophils, macrophages), complement proteins, and natural killer cells are part of innate immunity. Innate immunity provides immediate, nonspecific protection against a wide range of pathogens. Species resistance is a broader term that refers to the inherent ability of a particular species to resist infection by certain pathogens. Adaptive immunity is a specific immune response that is only activated upon exposure to a specific pathogen, and takes several days to develop. Microbial antagonism refers to the competition between different microorganisms for resources and space, which can limit the growth and colonization of pathogenic bacteria.