White blood cells (WBC) Leucocytes: Types , Neutrophil, Eosinophils, Basophils, Lymphocyte, Monocytes
Leucocytes (WBCs)
WBCs are the largest blood cells. Leucocytes make up only over 1% of the blood volume, Leucocytes and erythrocytes differ in several ways:
1. Each leucocyte has a nucleus, mitochondria, and other organelles, proving that they are actual cells.
2. There is no Hb in them.
3. Erythrocytes are not movable, although leucocytes are.
4. Leucocytes can exit veins and penetrate the surrounding tissue, while erythrocytes typically do not leave the vascular system.
5. The lifespan of the majority of leucocytes is relatively short.
WBC types
There are mostly two kinds:
1. Granulocytes, which are neutrophils, eosinophils, and basophils, have granules in their cytoplasm.
2. Agranulocytes, which include lymphocytes and monocytes.
1. Neutrophils (Polymorphonuclear leukocytes)
1. They are 12–15 µm in diameter, with a nucleus made up of 2–5 lobes, and they make up 60–70% of all circulating leukocytes.
2. There are two major kinds of granules in the neutrophil’s cytoplasm: azurophilic granules and specialized granules.
3. Small granules called specific granules contain lysozyme, collagenase, lactoferrin, alkaline phosphatase, and several non-enzymatic antibacterial proteins.
4. Acid phosphatase, αmonosidase, myeloperoxidase, lysozyme, cationic antimicrobial proteins, collagenase, elastase, nucleotidase, and other enzymes are found in azorophlic granules, which are lysosomes.
5. Neutrophils have a brief half-life of 1-6 hours in blood and 1-4 days in tissues.
6. Neutrophils can phagocyte germs and other tiny particles.
7. The formation of hydrogen peroxide (H2O2-) and superoxide (O2-) during phagocytosis kills bacteria.
8. O2 combined with myeloperoxidase creates a potent killing mechanism.
Eosinophils
1. The eosinophils make up 2-4% of the leukocytes in normal blood.
2. The lifespan of a life span in circulation is roughly ten hours and ten days in tissues
3. These cells’ nuclei are bilobed.
Large granules that are stained by eosin are found in the cytoplasm of eosinophils. These granules include a variety of enzymes, including phospholipase, RNAase, peroxidase, and others, in addition to a protein known as the major basic protein. Parasitic worms can be killed by this protein.
4. Both allergic reactions and parasitic infections are linked to an increase in the blood’s eosinophil count.
3. Basophils
Basophils comprise less than 1 per cent of leukocytes in the blood.
1. There are roughly 12 to 15 µm.
2. The nucleus is S-shaped or divided into uneven lobes.
3. The cytoplasm is stained with a basic dye and contains very big granules.
4. The granules’ primary constituents are heparin and histamine. These cells are crucial in the allergy process.
Lymphocyte
Lymphocytes are spherical cells; their diameters range from 6 to 8 µm for small lymphocytes to up to 18 µm for large lymphocytes.
1. Lymphocytes have big, rounded nuclei.
2. The tiny lymphocytes have very little cytoplasm, which in a blood smear looks like a narrow border around the nucleus. It is also slightly bit basophilic.
3. The lifespan of lymphocytes varies; some just last a few days, while others endure for many years.
4. All types of lymphocytes are linked to immune responses in protecting against invasive bacteria, foreign macromolecules, and cancer cells.
5. Lymphocytes are categorized based on their function, including B, T, and natural killer cells.
Monocytes
These are the largest white blood cells, and their nucleus has a kidney-like or horseshoe-like structure.
1. Monocytes have basophilic cytoplasm that contains lysosomes, which are extremely tiny azurophilic granules.
2. Blood monocytes move into the tissues and mature into macrophages, which consume big cells and ingest infections and debris.
3. While the life duration in the tissues is 60–120 days, it is only a few days in the circulation.
4. They make up 4–11%.
5. Monocytes primarily perform phagocytosis, but they can also secrete chemicals such as interlukins, such as interlukin 1 (IL-1).
6. The roles of macrophages in immunity and inflammation are significant.