Impacts and Significance of white blood cell counts in lymphocytic and Neutrophilic species

Introduction

Blood Cells

Blood cells are cell that are mainly found in blood, and produced via hematopoiesis. While the liquid component of blood, plasma, make up 55% of the blood, blood cells make up 45% , and can be categorized into 3 different groups (1). Erythrocytes, Thrombocytes, and Leukocytes. Leukocytes are white blood cells that are in charge for immunological response, and can be differentiated to granulocytes and agranulocytes. *

• Granulocytes are characterized by the presence of granules in their cytoplasm (2). The most abundant type of granulocytes are neutrophil granulocytes, then low number of eosinophil granulocytes, basophil granulocytes, and monocytes comprises granulocytes. Granulocytes are also known as polymorphonuclear leukocytes for their varying shape of nucleus

• Agranulocytes, which only contain a single nucleus in its cell, has its varying name mononuclear leukocytes. Opposite to granulocytes, they’re characterized by the absence of granules in the cytoplasm. There are two types of agranulocytes: lymphocytes and monocytes.

Neutrophil Granulocytes

Normal neutrophil morphology is similar in common domestic mammalian species. The chromatin of the nucleus is condensed and segmented and stains blue to purple. Nuclear lobes may be joined, but generally there is simply a narrowing of the nucleus between lobes without true filament formation (3).

Band neutrophils, which are the most common type of immature neutrophil seen in blood, is one stage less mature compared to segmented neutrophils. They can be distinguished from matures by the shape of their nucleus, lacking the clear segmentation (5).

Heterophils are are the most common leukocyte in avian blood and are analogous with mammalian neutrophils, however their nuclei aren't as lobulated (8).

Lymphocytes

Lymphocyte morphology can be characterized by its pale blue color of the cytoplasm and their nuclei are usually round or oval, allowing some slight indentation. Most of the lymphocytes that circulate in healthy dogs, cats, camelids and horses are small cells that have round nuclei with dense chromatin and a small rim of light blue cytoplasm. The chromatin is so dense because it is mostly heterochromatin (the cell is not actively transcribing DNA) (3).

WBC Counts

White Blood Cell count (WBC count) is an important subset of the complete blood count (CBC), as the number of leukocytes in the blood is often an indicator of disease (4). The WBC count is the total number of leukocytes in a given volume of blood. This count can be performed either manually or by automated cell counters.

The differential white blood cell count measures the percentage of each leukocyte subtype in an individual’s blood. It is performed by counting and identifying 200 consecutive leukocytes in a single drop of blood.

The absolute count for each leukocyte subtype can then be calculated by multiplying the differential by the total white blood cell count (6).

Total white blood cell counts in adult domestic animals (× 10*9 /l)

According to the ratio of lymphocytes and neutrophil granulocytes in blood circulation, species can be categorized into two groups: Lymphocytic and neutrophilic species, where lymphocytic species yield higher amount of lymphocytes compared to neutrophil granulocytes and vice versa for neutrophilic species. Species such as cattle, swine, sheep, and domestic fowl are considered to be lymphocytic species, where neutrophilic species are horse, dog, and cat.

Impacts and Significance of WBC Counts

Changes in white blood cell counts can indicate many alternations occurring within the body. The changes can be either physiological or pathological, and many reasons differ by the percentage of lymphocytes and neutrophils each species yield.