Leukocytes or WBCs in animals

Leukocytes or WBCs in animals

Leukocytes are large sized, nucleated cells, lesser in number and do not have hemoglobin content. These cells show polymorphic forms, which differ morpholog­ically and functionally.

Majority of the WBCs is larger than RBCs; while RBCs are present in millions per ml of blood, the WBCs are present in thousands per ml of blood.

The ratio of WBC to RBC varies from 1:100 in chicks to 1:1300 in goats, 1:600 in dog and cat, 1:800 in cattle 1:1000 in horse 1:1200 in sheep and 1:700 in man.

Site of production of WBCs

The granulocytes and the megakaryocytes are produced from the myelo­cytes of the bone marrow hence often referred as myeloid series of blood cells. The lymphocytes and the plasma cells are formed from the lymphoid tissues such as lymph nodes, spleen and lymphoid tissues of the bone marrow, gut etc. The monocytes are produced by the mononuclear phagocytic system (MPS) cells of spleen and bone marrow (reticuloendothelial system cells).

Types of leukocytes

Based on the staining nature of the cytoplasmic granules when subjected to Leishman’s stain, leukocytes are classified as granulocytes‚ which are further classified into three groups the neutrophils, eosinophils and basophils.

Some of the leukocytes have cytoplasmic granules but they are non-visible even after staining with Leishman’s stain, hence they are known as agranulocytes. The lymphocytes and monocytes form two groups of this type.

Normal values of leucocytes in domestic animals