Platelets are derived from megakaryocytes, cells produced in bone marrow, kidney, liver, and spleen, with large, lobed nuclei. Platelets are formed within the cell and then released into plasma. Erythrocytes (mature red blood cells), plasma cells (a type of B cell) and progranulocytes (precursors to neutrophils, basophils, and eosinophils) take no part in the creation of platelets, which are fragments of cells, not whole cells.

Lymphocytes are the second most common class of white blood cells, making up 26-33% of white blood cells.

Macrophages consume bacteria, cancer cells, and cellular debris via phagocytosis. Once these elements are within the cell, the macrophage is able to use lysosomes to break them down and prepare them for release into the blood as waste, which will eventually be excreted.

Diapedesis, also known as leukocyte extravasation, is the process by which white blood cells move into and out of blood vessels. This process includes four stages: chemoattraction, rolling adhesion, tight adhesion, and endothelial transmigration. This process is integral in the delivery of white blood cells to sites of infection and in their return into the blood stream to mobilize and facilitate the excretion of waste.

Monocytes, the largest of all the leukocytes, make up just 2-10% of the average white blood cell count. These white blood cells will mature into macrophages to phagocytose foreign matter.

The three main types of proteins in the blood are albumin, globulin, and fibrinogen. Major histocompatibility complex is not a free plasma protein, but rather a class of proteins found on the surface of all nucleated cells (MHC class I) and on the surface of certain immune cells known as antigen-presenting cells (MHC class II). They play an important part in immune function by displaying foreign antigens for communication between leukocytes.

Eosinophils are the leukocytes that are largely responsible for response to parasitic infections and allergies. They make up 1-3% of the average white blood cell count. They form the second smallest population of white blood cells, after basophils, which normally make up less than 1% of white blood cells in whole blood.

Neutrophils are the most common type of white blood cell, making up 55-70% of the total white blood cell population in the average blood sample.

Neutrophils, eosinophils, and basophils are all granulocytes, meaning they contain visible granules within their cytoplasms. These granules contains acids and antimicrobial enzymes, and are released at the site of infection. Monocytes and lymphocytes are agranulocytes, meaning they do not contain granules in their cytoplasm but rather destroy foreign proteins by other means, such as phagocytosis and cytotoxicity.

The only anucleate blood cells are erythrocytes, or red blood cells. These cells are created with nuclei, but each daughter cell will then lose its nucleus in order to create more suface area for hemoglobin to bind oxygen and for easier passage through narrow capillaries.