I spat onto a microscope slide and observed it at 1000x magnification with a Differential Interference contrast microscope to reveal a world of biological wonder.
Buccal epithelial cells from my cheek mucosa float by. The nuclei (defined round structures within the cell) hold my genome, and thus the genetic makeup for my entire body. The much smaller circle and rod shapes are bacteria from my human microbiota, a small selection of the billions of bacteria that I share my body with.
Buccal cells again but the round cell towards the middle (again with a clearly visible nucleus) is a neutrophil. This white blood cell forms part of my innate immune system and they quickly congregate at a focus of infection in order to kill invading pathogens. Neutrophils play a key role in the front line defence against bacteria and can kill pathogens by phagocytosis (ingestion), degranulation (release of antibacterial compounds) and neutrophil extracellular traps (networks of fibres made mostly from DNA)
A cluster of neutrophils (towards bottom right) fizzing with antibacterial intent. Neutrophils are a type of cell called a granulocyte as they clearly have granules in their cytoplasm. These granules contain antimicrobial cocktails that are used to kill pathogens. Low counts of neutrophils are termed neutropenia, a condition that makes individuals highly susceptible to infection. Neutropenia, can be congenital, a result of various blood disorders, or induced as a side effect of chemotherapy.