EXPRESSION OF TUMOR-NECROSIS-FACTOR-ALPHA (TNF-ALPHA) RECEPTORS AND SELECTIVE EFFECT OF TNF-ALPHA ON THE INNER CELL MASS IN MOUSE BLASTOCYSTS

The presence of tumor necrosis factor-alpha (TNF alpha) receptors was demonstrated at the cell surface of mouse blastocysts by indirect immu nofluorescence. Amplification of total cDNA from these embryos indicat ed that only the p60 form of the TNF alpha receptor was expressed. Amp lification of the p80 form remained negative. Blastocysts were culture d with 0.5, 5.0, or 50 ng/ml TNF alpha and examined for their morpholo gy and cell proliferation rate. Doses of 5.0 and 50 ng/ml delayed the morphological development after 24 h, but this effect was no longer de tected after 48 h. Overall cell proliferation was decreased by 15% wit h 50 ng/ml TNF alpha after 24 h and with all three concentrations afte r 48 h. Differential staining of the two embryonic cell lineages revea led that the reduction in cell number was at the expense of the inner cell mass, the cell group responsible for forming the fetal layers aft er implantation. This inhibition was not mediated by cytotoxicity, as the proportion of dead ICM cells remained low in the presence of ThF a lpha. Our data indicate that the expression of TNF alpha receptors is developmentally regulated before implantation, and that preimplantatio n embryos are responsive to TNF alpha.