THE NUMBER AND DISTRIBUTION OF HEPATIC NATURAL-KILLER-CELLS (PIT CELLS) IN NORMAL RAT-LIVER - AN IMMUNOHISTOCHEMICAL STUDY

Pit cells are a unique population of cells in sinusoids and peripheral blood, which can be considered natural killer (NK) cells with large g ranular lymphocyte (LGL) morphology. The aim of this study was to inve stigate the use of the monoclonal antibody (MAb) 3.2.3 as a specific m arker of rat pit cells to detect their number and distribution in the liver. The number of 3.2.3-positive cells was comparable to the number of LGL in liver low-density (LD) and high-density (HD) pit cell fract ions and in blood lymphocytes (P > .05). Immunoelectron microscopy sho wed that nearly all LGL in hepatic LD and HD and in blood fractions we re 3.2.3 positive. Using MAb 3.2.3 immunoperoxidase staining, the mean number of pit cells in liver frozen sections was determined to be 13. 7 +/- 1.1/mm(2). The number of pit cells was similar in the different liver lobes (P > .05). Reduced nicotinamideadenine dinucleotide (NADH) oxidase histochemical staining, to visualize a portal to central vein gradient, combined with immunostaining was used to analyze the lobula r distribution of pit cells. We found that 61.3% (17.1/mm(2)) of pit c ells were in the periportal area and 38.7% (10.8/mm(2)) in the central area. We conclude that MAb 3.2.3 can be used as a specific marker of rat pit cells and therefore can be used to quantify rat pit cell numbe r in various experimental models.