Encyclopedia of Health and Medicine

N
natural killer (NK) cell A granular LYMPHOCYTE
(white BLOOD cell with granules in its cytoplasm)
that has cytotoxic (cell-killing) functions within
the IMMUNE RESPONSE. NK cells belong to the CELL-
MEDIATED IMMUNITY pathway of the immune
response and do not require ANTIGEN presentation
to target a cell for destruction. NK cells are particularly
involved in killing tumor cells. They release
molecules that puncture or perforate (make
molecular holes in) the cell membrane of the cell
under attack. This assault may directly kill the cell
or cause accelerated APOPTOSIS (planned cell death)
that the target cell itself initiates in response to the
damage it experiences.
For further discussion of natural killer cells
within the context of the structures and functions
of the immune system, please see the overview
section “The Immune System and Allergies.”
See also ANTIBODY-MEDIATED IMMUNITY; B-CELL
LYMPHOCYTE; MACROPHAGE; T-CELL LYMPHOCYTE.
nonsteroidal anti-inflammatory drugs (NSAIDs)
Medications that relieve INFLAMMATION by suppressing
the action of PROSTAGLANDINS, which are
responsible for the inflammatory response. There
are several types of prostaglandins, most of which
are biochemical messengers that have numerous
roles in routine cellular activity. Other
prostaglandins are the agents of inflammation.
The prostaglandins that incite inflammation do so
by summoning numerous other biochemicals to
the site of an injury, ultimately resulting in fluid
accumulation and swelling at the site.
Three NSAIDs are available in over-the-counter
(OTC) preparations as well as stronger prescription-only
products: ibuprofen, naproxen, and
ketoprofen. All other NSAIDs available in the
United States (except aspirin) require a doctor’s
prescription.
NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS)
aspirin
diclofenac
diflunisal
etodolac
fenoprofen
flurbiprofen
ibuprofen
indomethacin
ketoprofen
meclofenamate
mefenamic acid
meloxicam
naproxen
oxaprozin
nabumetone
piroxicam
sulindac
tolmetin
How These Medications Work
NSAIDs work by blocking the action of cyclooxygenase
(COX), the enzyme that allows cells to
convert arachidonic acid (a dietary fatty acid
found in meats) into prostaglandins. The two
main forms of COX are cyclooxygenase 1 (COX-1)
and COX-2. Many types of cells in the body contain
COX-1, but COX-2 occurs primarily in mast
cells. COX-1 is responsible for prostaglandin synthesis
for these roles. Prostaglandins are also the
agents of inflammation. Mast cells contain COX-2,
which enables them to synthesize large quantities
of prostaglandins during an IMMUNE RESPONSE.
Most NSAIDs are nonselective; they block both
COX-1 and COX-2. Though this action effectively
relieves inflammation and associated symptoms
(such as PAIN and FEVER), it also interferes with
various general functions of cells throughout the
body. One consequence of this interference is
STOMACH upset. Gastric cells contain an abundance
of COX-1 and synthesize forms of prostaglandin
that help protect the lining of the stomach. Suppressing
COX-1 activity reduces this protection. As
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