According to Healthline, "A blood cell disorder is a condition in which there’s a problem with your red blood cells, white blood cells, or the smaller circulating cells called platelets, which are critical for clot formation. All three cell types form in the bone marrow, which is the soft tissue inside your bones. Red blood cells transport oxygen to your body’s organs and tissues. White blood cells help your body fight infections. Platelets help your blood to clot. Blood cell disorders impair the formation and function of one or more of these types of blood cells".
The red blood cells, known as erythrocytes, transport oxygen from the lungs to all parts of the body. The white blood cells, granular or agranular, are collectively labelled leukocytes and serve to fight off infections and protect the body from disease. They comprise (1) basophils, which secrete chemicals that promote the inflammatory reaction in the body; (2) eosinophils, which engulf antibody-labelled substances and also promote inflammation; (3) neutrophils, which capture and destroy foreign bacteria; (4) monocytes, which may be circulating in the blood stream or located in the tissues, where they are known as macrophages and capture and destroy bacteria and other foreign substances and remove dead cells from the body; (5) lymphocytes, which are responsible for specific immune responses to viruses and foreign substances within the body, including cancer cells, and include: B-cells (antibody immunity), T-cells (cell-mediated immunity) of three types - cytotoxic T-cells, helper T-cells and suppressor T-cells, and NK-cells (natural killer cells). The platelets, also called thrombocytes, assist the blood in clotting. The blood cells are primarily formed in the bone marrow, though some white blood cells, notably leukocytes, may also be produced in organs of the lymphatic system, such as the spleen, thymus and lymph nodes.