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 morphological aspect, we evaluated electron-microscopically the frequency of 0.2 m vesicles (rod-cored and empty vesicles) and dense granules in LGL from the liver, spleen, and peripheral blood of the rat. Both of these cell organelles are characteristic to LGL and may relate to natural killer-mediated cytolysis. On the average, there were 12.7 of the 0.2 m vesicles and 4.3 rod-cored vesicles (RCV) per cell section in the liver, 6.6 0.2 m vesicles and 1.6 RCV in the spleen, and 8.6 0.2 m vesicles and 0.9 RCV in the peripheral blood. The number of 0.2 m vesicles per cell section ranged from 0 to 19 with the exception of a few higher instances. Therefore, LGL were divided into vesicle-rich(>9 0.2 m vesicles per cell section) and vesicle-poor (<8 per cell section) populations. Hepatic LGL consisted mainly of a vesicle-rich population while splenic LGL consisted mainly of a vesicle-poor population, and peripheral blood contained equal proportions of both populations. In addition to diversity with regard to the number of 0.2 m vesicles, LGL obtained from various organs also displayed heterogeneity in the number and size of dense granules. Since the number of dense granules per cell section usually ranged from 1 to 13, LGL were diveded into 2 populations, i.e., LGL with many (>7 per cell section) granules and those with a few(<6 per cell section) granules. Specifically, splenic LGL had a few small (average diameter, less than 400 nm) dense granules, while sections of LGL from the liver and peripheral blood displayed many small dense granules and a few large (>400 nm) ones, respectively, in addition to the populations seen in the spleen. Thus, the present study has demonstrateda difference in the distribution of 0.2 m vesicles in LGL based on the tissue of origin. The present study has revealed the difference in the distribution of 0.2 m vesicles of LGL by tissue and indicated that immature LGL are predominant in the spleen, while hepatic LGL are generally more mature as defined by the number of vesicles. These data suggest that the microenvironment of the liver may contribute to the increased expression of these vesicles in LGL.