IMMUNOHISTOCHEMICAL ANALYSIS OF HUMAN EMBRYOS AND FETUSES - AN INSIGHT INTO THE MECHANISM OF SUBVERSION OF ANTIGENIC DIFFERENTIATION IN NEOPLASIA

Objectives.-Immunohistochemical identification of intermediate filamen ts and other cell identity markers is of immense value in diagnostic t umor pathology. However, the literature contains many examples of inap propriate expression of markers by various tumors or coexpression of t wo or more markers supposedly specific for different cell types. The p resent study investigated this subversion of antigen differentiation i n tumors by using developing tissues as a model.Materials and Methods. -Twenty-five human embryos and fetuses of 4 to 24 weeks' gestation wer e studied. An indirect immunoperoxidase method was applied to formalin -fixed, paraffin-embedded sections using a panel of 13 commonly used c ell identity markers including intermediate filaments. Results.-During early development, vimentin was found to be coexpressed with cytokera tin in surface ectoderm, developing notochord, renal tubule epithelium , and intestinal mucosa. It coexpressed with glial fibrillary acidic p rotein in developing neuroglial tissue, with S100 in cartilage, and wi th skeletal muscle markers in myotubules. Hence, vimentin represents i mmaturity of tissues and is coexpressed with specific cell markers to be eventually replaced by the latter. Transbarrier expression of cytok eratin in smooth muscle was also noted. Conclusion.-The aberrant expre ssion of antigens in neoplastic tissues, as reported in the literature , simulates the varying expression of antigens in immature tissues dur ing development. Hence, it is proposed that the phenomenon of antigeni c subversion in neoplasia is related to the process of maturation and differentiation.