ONTOGENY OF MILKY SPOTS IN THE HUMAN GREATER OMENTUM - AN IMMUNOCHEMICAL STUDY

Background: Milky spots in the human greater omentum are preformed spe cific accumulations of primarily macrophages within the stroma of the greater omentum, To obtain a better understanding of milky spots in th e human greater omentum, the development and the earliest forms of mil ky spots in the human greater omentum were studied, with special atten tion to the macrophage population Methods: Specimens of human greater omentum were obtained from fetuses of 20 to 40 weeks gestation and one newborn three days old (n = 6), Using mature macrophages (RFD 7), act ivated macrophages (RFD 1), B-lymphocytes (CD 22), and T-lymphocytes ( CD 2), and immunoperoxydase labeling, the percentage of these cells in developing milky spots and the development of milky spots were studie d by light microscopy, A time-dependent increase in the percentage of positive staining cells and the size of clusters was analyzed using th e non-parametric Spearman rank correlation test, Results: Small accumu lations of cells with about 50% monocytes/macrophages were present at 20 weeks of gestation, With increasing gestational age the number of c lusters of cells increased significantly (P < 0.01) as well as their s ize (P < 0.01), Starting at 29 weeks, vascularized clusters of cells w ere seen; true milky spots were present at 35 weeks, A significant (P < 0.05) increase in the percentage of mature macrophages was found in developing milky spots, whereas no activated macrophages were seen, Th e percentage of B-lymphocytes and T-lymphocytes found in the clusters of cells and milky spots increased significantly (P < 0.05) but did no t exceed 10% of the total number of cells, Conclusions: From our data it can be concluded that milky spots are specific structures in the gr eater omentum formed between the 20th and 35th week of gestation, Furt her, we concluded that immature cells (promonocytes) mature locally in developing milky spots. (C) 1997 Wiley-Liss, Inc.