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1362 Lymphocytes (Lymphocytosis, Lymphopenia) Lymphoma Flow Cytometry

Causes of Abnormally High Levels Next Diagnostic Steps to Consider Relative Cost: $$
Preovulation, ovarian cysts if Levels Are Low Pearls
VetBooks.ir Next Diagnostic Steps to Consider Lab Artifacts To facilitate ovulation timing, once visible signs
Evaluate for anestrus.
if Levels Are High
of estrus have begun and vaginal cytology reveals
A marked increase in serum LH concentra-
be measured daily to ensure detection of the
tion occurs approximately 48 hours before ELISA method: hemolyzed or lipemic samples > 70% cornified cells, serum LH levels should
should not be used; however, hemolysis does
ovulation. Progesterone concentration should not interfere with radioimmunoassay. preovulatory LH surge and optimal timing of
remain high if pregnancy has occurred. breeding/insemination.
Evaluation for cystic ovaries with abdomi- Specimen Collection and Handling Antimullarian hormone evaluation is better
nal ultrasound if inappropriate/persistent Serum, 1 mL. Collect blood in red top tube, for assessment of spay status or for ovarian
elevation spin, and collect serum. Sample should be free remnants.
of hemolysis and lipemia. Store at 2°C-4°C for
Causes of Abnormally Low Levels 24 hours; freeze for longer storage. Ship frozen AUTHOR & EDITOR: Lois Roth-Johnson, DVM, PhD,
Low values are associated with anestrus. or on ice. Cage-side test kits are also available. DACVP

Lymphocytes (Lymphocytosis, Lymphopenia)

Definition Causes of Abnormally High Levels Next Diagnostic Steps to Consider
The mononuclear leukocytes that mediate • Excitement/physiologic leukocytosis from if Levels Are Low
immune responses. Most lymphocytes are epinephrine release (especially young cats) Evaluate for causes listed, depending on clinical
small with condensed chromatin and scant • Lymphoid neoplasms (e.g., lymphoid signs.
basophilic cytoplasm, although very low leukemias, stage V lymphoma)
numbers have more cytoplasm with fine red • Inflammatory diseases with antigenic stimula- Drug Effects
to magenta granules clustered near nucleus tion (especially infections such as Ehrlichia Glucocorticoids cause lymphopenia by causing
(granular lymphocytes). On a blood smear, canis or Spirocerca lupi) sequestration of lymphocytes in lymphoid tissue
the nucleus of a small lymphocyte in dog • Hypoadrenocorticism (“relaxed” leukogram: and lympholysis (minor).
or cat is typically similar or slightly larger in lymphocytosis without neutrophilia in an
size compared to erythrocytes or smaller than obviously stressed animal, i.e., conspicuous Specimen Collection and Handling
neutrophils. absence of a stress leukogram) EDTA whole blood (lavender-top tube) and
freshly prepared blood smear for laboratory
Physiology Next Diagnostic Steps to Consider to stain
Lymphocytes migrate from blood into lymphoid if Levels Are High
tissues, circulate in the lymphatic system, and • Evaluate for causes listed, depending on Relative Cost: $$ (reported as part of CBC)
reenter the venous circulation via the thoracic clinical signs.
duct. Using surface receptors as markers, lym- • The PCR for antigen receptor rearrangement Pearls
phocytes can be classified as T lymphocytes (PARR) test evaluates clonality of T and B • In evaluating lymphocytosis, cell morphology
(e.g., CD3-positive) that mediate cell-mediated lymphocyte antigen receptor genes and is important. Markedly increased numbers of
responses, B lymphocytes (e.g., CD79a-positive) is a sensitive method to detect neoplastic large or atypical lymphocytes indicate acute
that mediate humoral responses, or natural killer lymphocytes. lymphoid leukemia/stage V lymphoma,
lymphocytes (null cells) that mediate cytotox- whereas a marked increase in small, well-
icity. Most of the circulating lymphocytes in Causes of Abnormally Low Levels differentiated lymphocytes occurs with chronic
blood are T lymphocytes. Granular lympho- • Endogenous or exogenous glucocorticoids lymphoid leukemia/stage V lymphoma or
cytes include cytotoxic T cells and natural (stress leukogram) non-neoplastic causes of lymphocytosis.
killer cells. • Acute inflammation (especially viral infections) • Neoplastic granular lymphocytes occur in blood
• Disruption of lymphatic flow (e.g., chylo- with lymphomas that usually originate in the
Reference Interval thorax, lymphangiectasia) small intestine of cats or liver/spleen of dogs.
3
Dogs: 1.0-5.0 × 10 lymphocytes/mcL; cats: • Immunodeficiency (e.g., severe combined
3
1.5-7.0 × 10 lymphocytes/mcL immunodeficiency) AUTHOR: Stephen D. Gaunt, DVM, PhD, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP

Lymphoma Flow Cytometry

Definition through an electronic detection apparatus; Physiology
Flow cytometry allows identification and quan- these cells interrupt (scatter) a signal, allow- Lymphoma is a neoplastic proliferation of
tification of specific cell populations in complex ing cell size and complexity to be measured. lymphocytes that can be categorized based on
fluids such as blood or aspirates of lymph node This method can be used to assist in the lymphocyte type (T cell vs. B cell) and cell size
or bone marrow. Cells in suspension are tagged diagnosis and subtyping of lymphoma, among (large cell vs. small cell). Membrane surface
with antibodies and then passed single-file other uses. molecules, marked by fluorescence-labeled

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