QUANTITATIVE-ANALYSIS OF ROD-CORED VESICLES AND DENSE GRANULES OF LARGE GRANULAR LYMPHOCYTES IN THE LIVER, SPLEEN, AND PERIPHERAL-BLOOD OF RATS

Large granular lymphocytes (LGL) comprise a natural defense system in the liver and exert an inhibitory effect on tumor cell metastasis. In order to demonstrate the maturation of LGL in the liver from the morph ological aspect, we evaluated electron-microscopically the frequency o f 0.2 mu m vesicles (rod-cored and ''empty'' vesicles) and dense granu les in LGL from the liver, spleen, and peripheral blood of the rat. Bo th of these cell organelles are characteristic to LGL and may relate t o natural killer-mediated cytolysis. On the average, there were 12.7 o f the 0.2 mu m vesicles and 4.3 rod-cored vesicles (RCV) per cell sect ion in the liver, 6.6 0.2 mu m vesicles and 1.6 RCV in the spleen, and 8.6 0.2 mu m vesicles and 0.9 RCV in the peripheral blood. The number of 0.2 mu m vesicles per cell section ranged from 0 to 19 with the ex ception of a few higher instances. Therefore, LGL were divided into ve sicle-rich (>9 0.2 mu m vesicles per cell section) and vesicle-poor (< 8 per cell section) populations. Hepatic LGL consisted mainly of a ves icle-rich population while splenic LGL consisted mainly of a vesicle-p oor population, and peripheral blood contained equal proportions of bo th populations. In addition to diversity with regard to the number of 0.2 mu m vesicles, LGL obtained from various organs also displayed het erogeneity in the number and size of dense granules. Since the number of dense granules per cell section usually ranged from 1, to 13, LGL w ere divided into 2 populations, i.e., LGL with many (>7 per cell secti on) granules and those with a few (<6 per cell section) granules. Spec ifically, splenic LGL had a few small (average diameter, less than 400 nm) dense granules, while sections of LGL from the granules and a few large (>400 nm) ones, respectively, in addition to the populations se en in the spleen. Thus, the present study has demonstrated a differenc e in the distribution of 0.2 mu m vesicles in LGL based on the tissue of origin. The present study has revealed the difference in the distri bution of 0.2 mu m vesicles of LGL by tissue and indicated that immatu re LGL are predominant in the spleen, while hepatic LGL are generally more mature as defined by the number of vesicles. These data suggest t hat the microenvironment of the liver may contribute to the increased expression of these vesicles in LGL.