MYELOMA; SIGNS AND SYMPTOMS OF CANCER; SMOKING
AND HEALTH; STAGING AND GRADING OF CANCER.
leukocyte A white BLOODcell, also referred to as
a WBC. Leukocytes are the foundation of the
body’s IMMUNE RESPONSEand are phagocytic—that
is, they have the ability to consume other cells.
They circulate in the blood and the LY M P Has well
as reside in tissues throughout the body. There are
three basic types of leukocytes: granulocytes,
monocytes, and lymphocytes. Each type has sev-
eral subtypes. The SPLEENand lymph tissues pro-
duce monocytes and lymphocytes; the red BONE
MARROWproduces granulocytes.
HEALTH CONDITIONS THAT AFFECT
LEUKOCYTE COUNTS
ALLERGYresponse ASTHMA
AUTOIMMUNE DISORDERS CHEMOTHERAPY
environmental toxin exposure HYPERSENSITIVITY REACTION
INFECTION INFLAMMATION
LEUKEMIA LEUKOPENIA
LYMPHOCYTOPENIA LYMPHOMA
many cancers medication side effects
MONONUCLEOSIS, INFECTIOUS RADIATION THERAPY
surgery vitamin B 12 deficiency
A healthy adult has between 5,000 and 10,000
leukocytes per microliter of blood, with granulo-
cytes accounting for about 70 percent. Increases in
certain subtypes of leukocytes suggest particular
health conditions. A substantial increase overall in
LEUKOCYTEcount may indicate a cancer of the bone
marrow such as LEUKEMIAor LYMPHOMA. The ratio
between erythrocytes (red blood cells) and leuko-
cytes in the blood is also an important diagnostic
indicator.
For further discussion of leukocytes within the
context of blood and lymph structure and func-
tion please see the overview section “The Blood
and Lymph.”
See also B-CELL LYMPHOCYTE; CELL STRUCTURE AND
FUNCTION; ERYTHROCYTE; HEMATOPOIESIS; PHAGOCYTO-
SIS; PLASMA; PLATELET; SIDE EFFECT; THYMUS.leukopenia A decline in the number of leuko-
cytes (white BLOODcells) circulating in the blood
to fewer than 4,000 leukocytes per microliter of
whole blood. The most common manifestation of
leukopenia is NEUTROPENIA, a shortage of granulo-
cytes called neutrophils. Most leukopenia is sec-
ondary to other health conditions a person may
have, such as viral infections or cancers that
involve the BONE MARROW, and circumstances, such
as CHEMOTHERAPY. Numerous medications can
cause leukopenia as an undesired SIDE EFFECTof
treatment. In such situations the doctor will eval-
uate the relative value of the inherent risks in
continuing or discontinuing the causative medica-
tion. Leukopenia lowers the body’s ability to resist
and fight INFECTION and when severe can allow
life-threatening infections to invade. Frequent or
unusual infections, especially persistent GINGIVITIS
or periodontitis, may suggest leukopenia. Treat-
ment targets any infection or other underlying
cause.
See also LYMPHOCYTOPENIA; PERIODONTAL DISEASE;
THROMBOCYTOPENIA.148 The Blood and Lymph
LEUKOCYTESType of Leukocyte Subtypes Organ that Produces
granulocytes basophils, eosinophils, neutrophils red BONE MARROW
monocytes macrophages (reside in the tissues) SPLEEN, lymph nodes
lymphocytes T-cell lymphocytes SPLEEN, lymph nodes, THYMUS
cytotoxic T-cells
helper T-cells
memory T-cells
suppressor T-cells
B-cell lymphocytes
memory B-cells
PLASMAcells