N

natural killer (NK) cell A granular LYMPHOCYTE
(white BLOODcell 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 ANTIGENpresentation
to target a cell for destruction. NK cells are partic-
ularly 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 sup-
pressing 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 prescrip-
tion-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 cyclooxy-

genase (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 con-

tain COX-1, but COX-2 occurs primarily in mast

cells. COX-1 is responsible for prostaglandin syn-

thesis 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

STOMACHupset. Gastric cells contain an abundance

of COX-1 and synthesize forms of prostaglandin

that help protect the lining of the stomach. Sup-

pressing COX-1 activity reduces this protection. As

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