White blood cells, also known as leukocytes, are usually too small to be seen with the naked eye. Though these microscopic components usually remain unseen, there are two distinct ways they can be observed. One method involves microscopic examination, allowing for detailed viewing. A unique physiological phenomenon also allows some individuals to perceive their own white blood cells.
What are White Blood Cells?
White blood cells are an important part of the body’s immune system, protecting against infection and disease. They circulate throughout the bloodstream and tissues, acting as a defense against foreign invaders. There are several types of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specialized roles in immune response. Although called “white,” these cells are colorless before being stained. They are also larger than red blood cells, which are far more numerous in the blood.
Microscopic Observation of White Blood Cells
The primary method for viewing white blood cells involves using a microscope. To prepare for observation, a small drop of blood is spread thinly onto a glass slide, creating a blood smear. The smear is then allowed to air dry. The dried blood smear is then stained with special dyes, such as Wright’s or Giemsa stain. These stains contain components like eosin and methylene blue, which bind to different parts of the cells, making them visible.
Under a high-power microscope, white blood cells become visible. They appear larger than surrounding red blood cells and possess a distinct, often multi-lobed or kidney-shaped nucleus, which stains blue or purple. The cytoplasm, material surrounding the nucleus, stains in varying shades of pink, orange, or blue, depending on the cell type and stain used. This staining process allows scientists and medical professionals to differentiate between white blood cell types based on their shapes, nuclear characteristics, and granular patterns.
The Blue Field Entoptic Phenomenon
Beyond microscopic examination, some individuals can perceive their own white blood cells without special equipment. This is known as the Blue Field Entoptic Phenomenon. It occurs when gazing at a uniform, bright blue light source, like a clear blue sky. The tiny, bright, darting dots observed are white blood cells moving through capillaries on the surface of the retina, the light-sensitive tissue at the back of the eye.
This phenomenon occurs because abundant red blood cells absorb blue light, creating a dark background in the retinal capillaries. White blood cells, being larger and less numerous, do not absorb blue light as effectively, allowing it to pass through or scatter. As these white blood cells navigate the narrow capillaries, they create momentary gaps or bright spots in the continuous stream of red blood cells, which the brain interprets as tiny, moving lights. These dots often appear to follow winding paths and may accelerate with each heartbeat, reflecting the pulse of blood flow in the capillaries. This visual experience is a normal physiological process and not a cause for concern.
The Importance of White Blood Cells in Health
White blood cells are fundamental to the body’s defense mechanisms and maintaining health. They are a vital part of the immune system, surveying the body for signs of infection or foreign substances. These cells identify and neutralize pathogens like bacteria, viruses, and fungi, preventing illness. White blood cells are important for mounting an effective response to threats, ensuring the body remains protected and functioning properly.