Histochemical localization of pregnancy-associated plasma protein A in fetal, infant, and adult organs and comparison between antisera.

Histochemical localization of pregnancy-associated plasma protein A (PAPP A) was performed on various genital and extragenital organs from fetuses, infants, and adults. Three types of PAPP A reactive cells were found: endocrine, epithelial, and hematopoietic cells. Positive endocrine organs included the decidua and the fetal adrenal and Leydig cells. Positive epithelial cells were found in actively proliferating tissues, such as fetal renal tubules, fetal intestinal mucosa, and adult proliferative endometrial glands. In bone marrow, red cell precursors were PAPP A positive. Comparison of a commercially available antiserum with one raised in our own laboratory revealed significant differences in histochemical staining. The biological relevance of these findings remains to be determined.