Effects of BCG Treatment on the Mouse Thymic Cortex : An Electron Microscopic Study

Ko, Jung Sik; Ahn, Eui Tae; Park, Gyung Ho; Woo, Sung Im; Han, Young Bok; Gyung, Hong Gee

Abstract

This experiment was performed to study the morphological responses of the thymic cortex of the mice after administration of BCG. Healthy adult mice weighing 25gm each were divided into normal and experimental groups. BCG[0.03X108-0.32X108 CFU] were injected subcutaneously to the animals every other day, and animals were sacrificed at 4 days, 1 week, 2 weeks and 8 weeks following the first injection. Thymus were removed immediately after sacrifice and transferred to cold phosphate buffered 2.5% glutaraldehyde-1.5% paraformaldehyde solution[pH 7.3], and cut into small pieces. Tissue samples were fixed for 2-3 hours in the same fixative, postfixed with phosphate buffered 1% osmium tetroxide solution[pH 7.3], dehydrated in a graded series of alcohol, and embedded in araldite mixture. Ultrathin sections stained with uranyl acetate and lead citrate were observed with a JEM 100CX-II electron microscope. The observed results were as follow : 1. In the early BCG treated groups, a few eosinophile leucocytes were observed, but more eosinophils were observed in later groups. Some elongated and bar-shaped lysosomes with eletron lucent gap were often obserced in the macrophages. 2. Cortical population of thymocytes in the thymus were reduced, whereas territoris of the epithelial reticular cells were expanded especially in 2 weeks and 8 weeks groups. Some portion of the thymic cortex exhibited large intercellular spaces, and a few nuclear bodies filled with materials of medium density were observed in the epithelial reticular cells. 3. In the 8 weeks groups, macrophages, plasma cells and eosinopile leucocytes and developing eosinophile leucocytes were often observed in the thymic cortex. Distended cisternae of granular endoplasmic reticula and newly forming prosecretory granulses in the Golgi complex were ovserved in som plasma cells. From the above results, it was suggested that repeated treatment with BCG could induce disturb the maturation and differentiation of the T lymphocytes. In turn, BCG, if repeatedly injected, may disturb the immunological medchanism.