Deficiency of blocking factors in intrauterine growth retardation and its relationship with chronic villitis.

We tested sera from 22 women and their singleton full-term infants for inhibition in one-way mother/father mixed lymphocyte culture (MLC). Ten of these infants were small for gestational age (SGA) and 12 of them adequate for gestational age (AGA). Twenty placentas from these cases (ten from SGA infants and ten from AGA infants) were histologically studied. The results show evidence that blocking factors capable of inhibiting responses of wife's lymphocytes to husband's cells in MLC are present in sera from women with normal pregnancies but not in women with SGA infants. Sera from AGA infants showed a blocking activity on responses of husband's lymphocytes to wife's cells and this was not observed in sera from SGA infants. Lesions of chronic villitis were found in six placentas from SGA infants and in none from AGA infants. A deficit of blocking protective factors and its relationship with placental lesions is in favor of an immunological mechanism for intrauterine growth retardation.