Biology of the neonate
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Using the immunoperoxidase method, major changes in the distribution of lysozyme (LZM) were found to occur during fetal development. At 10 weeks of gestation LZM was detected for the first time in the proximal tubules of the kidney. This generally coincides with the reported appearance of LZM in fetal blood and amniotic fluid. ⋯ At about 18--20 weeks, LZM-positive mononuclear cells were detected in other tissues tested, such as liver, spleen and thymus. Paneth cells were found to be specifically stained at about 20 weeks of gestation. The timing of the appearance of LZM in the various tissues is discussed in relation to the functional maturation of each organ and the ontogeny of this enzyme in other species.