Video Transcript
Which statement does not describe
the response of the nonspecific, innate, immune system? (A) It triggers complement proteins
in the blood plasma. (B) It leads to inflammation
following tissue injury. (C) It involves neutrophils and
macrophages. (D) It is an immediate response to
infection. (E) Cells of this system are
antigen-specific.
The immune system is a network of
cells and proteins that defend us against infection. It can be divided into innate, or
nonspecific, immunity and adaptive, or specific, immunity. Since this question is asking about
innate immunity, let’s go over some of its features and eliminate answer choices as
we go along.
Innate immunity is the first line
of defense while the adaptive response develops. It is immediate and includes
barriers like our skin that can prevent pathogens from entering and causing
infection. Our statement is asking us to find
a statement that does not describe innate immunity. So we can eliminate answer choice
(D).
For pathogens that enter our body,
such as bacteria through a cut, for example, inflammation of that area can take
place. We’ll describe inflammation in a
bit of detail. But first let’s eliminate answer
choice (B) since inflammation is a feature of the innate immune system.
Inflammation is characterized by
swelling of the site of injury. This is due to the accumulation of
fluid that contains immune cells, such as neutrophils and macrophages, that can
destroy the invading pathogens by engulfing them by phagocytosis. We can now eliminate answer choice
(C).
Another way the innate immune
system functions is through the complement system. Complement is a collection of
proteins that circulate in the blood plasma that can bind to pathogens directly or
in combination with antibodies from the adaptive immune response. Complement can destroy pathogens in
different ways. But one way is that it can assemble
on the surface of bacteria to form a pore that causes the bacteria to lyse. So now we can eliminate answer
choice (A).
The innate immune response is
nonspecific. This means that it targets all
pathogens in the same way. But some pathogens have developed
ways around the innate immune response and require a more specific approach. This is where the adaptive immune
response comes in. The adaptive immune response
targets pathogens very specifically by building a response against that particular
pathogen. It can do this by recognizing
proteins on the pathogen’s surface, called antigens, that make that pathogen
unique.
Therefore, the statement that does
not describe the innate immune system is given by answer choice (E). Cells of this system are
antigen-specific.
