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In most cells the genetic material (DNA) is housed in a single, rounded nucleus. Certain immune cells—neutrophils, eosinophils, basophils, and mast cells—package their DNA into multiple smaller spheres, creating a multilobed or lobular nucleus. This unique architecture is key to their rapid response and specialized functions.
The lobes are composed of chromatin, a complex of DNA and histone proteins. DNA winds around histone octamers, forming nucleosomes that resemble a pearl‑necklace. Additional structural proteins fold the nucleosomes into dense, ball‑shaped clumps. In ordinary cells this results in one large nucleus; in granulocytes it produces several discrete, teardrop‑shaped lobes.
Beyond packaging, chromatin influences gene transcription and translation. In certain immune cells, it also participates in NETosis—a defense mechanism where DNA is expelled to trap and kill pathogens.
Granulocytes are the class of immune cells that exhibit multilobed nuclei. They include neutrophils (the most abundant white blood cell, comprising 60–70% of circulating leukocytes), eosinophils, and basophils. Mast cells, though not granulocytes, also possess lobular nuclei.
Neutrophils can exhibit more than four lobes—a condition known as hyper‑segmentation—when the body lacks vitamin B12, folic acid, or iron. A study in the journal Pediatric Hematology and Oncology found that 81% of iron‑deficient children had hyper‑segmented neutrophils, compared to only 9% of healthy peers.
One of the most striking functions of lobulated nuclei is the ability to eject chromatin into the extracellular space, forming neutrophil extracellular traps (NETs). During NETosis, a neutrophil sacrifices itself, releasing sticky DNA strands decorated with antimicrobial proteins that ensnare and kill bacteria, fungi, and other invaders.
This mechanism underscores the dual role of chromatin: as a genomic organizer inside the cell and as an active antimicrobial agent outside the cell.
