THE MOUSE CHIMERA DURING INTRAUTERINE STAGES - IMMUNOHISTOCHEMICAL ANALYSIS WITH THE C3H STRAIN-SPECIFIC ANTIBODY

Our objective was to establish an immunohistological method for analys is of chimerism in mouse chimeras at embryonic stages with an anti-C3H strain-specific antigen (CSA) antibody. We developed an effective new method to retain CSA antigenicity with good morphology of embryonic t issues by using microwave irradiation (MWI) for pre-fixation, 95% etha nol/1% acetic acid as post-fixative solution, and polyester wax as emb edding material. We used a biotinylated mouse monoclonal anti-CSA anti body, peroxidase-avidin, and silver amplification. These procedures we re successful in demonstrating the chimerisms in various tissues of C3 H<-- -->Balb/c chimeras at different embryonic stages and postnatal da ys. In chimeras at Days 7 and 7.5 post coitum (p.c.), both genotypes w ere clearly identified and well intermingling in every embryonic tissu e (embryonic ectoderm, mesoderm, extra-embryonic ectoderm, ectoplacent al cone, amnion, and chorion). Chimerisms at Day 14.5 p.c. were also c learly observed in mesencephalon, neural retina, spinal cord, lung, ki dney, and liver. We concluded that the present immunohistological proc edures for analysis of chimerism during embryonic periods will give us insightful information about dynamic histological changes such as cel l proliferation, migration, selection, and death during organogenesis.