Question

Choose the false statement about nonspecific defenses:

a. Complement functions protectively by being converted into histamine which activates immune cells.
b. Histamine increases permeability of capillaries so that WBC's can more readily reach the infection site.
c. Opsonization enhances phagocytosis.
d. Fever and inflammation are both beneficial innate defenses.
e. Macrophages may engulf an antigen, degrade it, and then present the epitope to other immune cells.

Answer 1

The incorrect statement about nonspecific defenses is that complement proteins convert into histamine which activates immune cells; in fact, they mark pathogens and form lytic complexes.

Step-by-step explanation:

The false statement about nonspecific defenses is a. Complement functions protectively by being converted into histamine which activates immune cells. Complement proteins are part of the innate immune system and perform several functions integral to defending the body against pathogens. Their role includes marking pathogens for phagocytosis (opsonization) and forming membrane attack complexes that result in the lysis of microbial cells.

Complement proteins do not convert into histamine. Histamine is released by mast cells and basophils and plays a crucial role in inflammation by increasing the permeability of capillaries, which allows white blood cells (WBCs) to access the infection site more easily, as stated in b. Further, option c is true as opsonization indeed enhances phagocytosis, and option d is accurate as both fever and inflammation serve as beneficial innate defenses. Lastly, option e correctly describes the function of macrophages in antigen presentation.