Medical Electron Microscopy

, Volume 37, Issue 1, pp 29–36

Pit cells as liver-associated natural killer cells: morphology and function


    • Department of Anatomy, Graduate School of MedicineOsaka City University
  • Kenji Kaneda
    • Department of Anatomy, Graduate School of MedicineOsaka City University
  • Shuichi Seki
    • Department of Hepatology, Graduate School of MedicineOsaka City University
  • Yuji Nakajima
    • Department of Anatomy, Graduate School of MedicineOsaka City University
SPECIAL REVIEW SERIES: Hepatic sinusoidal cells in liver physiology and pathology

DOI: 10.1007/s00795-003-0229-9

Cite this article as:
Nakatani, K., Kaneda, K., Seki, S. et al. Med Electron Microsc (2004) 37: 29. doi:10.1007/s00795-003-0229-9


Pit cells are one type of hepatic sinusoidal cells, defined morphologically as large granular lymphocytes (LGLs) and functionally as liver-associated natural killer (NK) cells. They are situated inside the sinusoidal lumen, adhering to the endothelial cells and Kupffer cells. They contain multivesicular body-related dense granules and rod-cored vesicles. The number and size of granules and vesicles differ between hepatic NK cells and peripheral blood cells, suggesting possible differentiation of the latter into the former in the microenvironment of the liver. In addition to NK cells, natural killer T (NKT) cells are also abundant in the liver. They share several morphological properties with NK cells, and at least some are probably observed as pit cells under an electron microscope. NK cells recognize target cells with their surface receptors such as inhibitory and activating receptors. They exert antitumor functions by exocytosis of perforin/granzyme-containing granules, induction of death receptor-mediated apoptosis in target cells, and production of various cytokines that augment the activities of other immune cells. NKT cells play important roles in initiating and assisting the function of NK cells by producing interferon-gamma.

Key words

Pit cellsNK cellsNKT cellsLGLLiver
Download to read the full article text

Copyright information

© Springer-Verlag Tokyo 2004