Immunological study of expression of CD1 in preimplantation and midgestation mouse embryo cells and placental trophoblasts and the role of decidual natural killer T cells at the feto-maternal interface

ABSTRACT

Expression of major histocompatibility complex molecules in the preimplantation embryo is important for control of development and immune recognition of the embryo by the mother. Four types of major histocompatibility complex class I molecules that have been identified are as follows class Ia, class Ib, class Ic, and class Id. Expression of class Ic and class Id antigens in preimplantation embryos has not yet been fully evaluated. Cluster of differentiation 1 [CD1] molecule is a member of class Id antigen. Localization and regulation of CD1 expression remain unclear. The aim of this study was to detect expression of the CD1 molecule in a preimplantation mouse embryo at two-cell, four-cell, eight-cell, and blastocyst stages and in the embryo cells and placental trophoblasts at 10 days of gestation. Detection of invariant natural killer T [iNKT] cells in the decidua at the site of attachment of the placenta was also investigated. Mice of the C57BL/6 genetic background were used. Forty-eight female and 16 male mice of 10-12 weeks of age were divided into two groups. Group 1 included 24 female and eight male mice. Eight breeding colonies were constructed in which each cage contained one male and three female mice. The pregnant female mice were killed at 36, 48, 60, and 80 h of appearance of the vaginal plug to collect two-cell, four-cell, eight-cell, and blastocyst stages of embryos, respectively. The embryos were then processed for immunohistochemistry. Group 2 animals included 24 female and eight male mice. Eight breeding colonies were constructed in which each cage contained one male and three female mice. The pregnant female mice were killed at 10 days of gestation when embryo cells, placental cells, and decidual cells were isolated and processed for culturing and immunohistochemistry. This study showed no expression of CD1 molecules in any of the preimplantation mouse embryo stages till the blastocyst stage, but were detected on the cell surface and inside the cytoplasm of embryo cells and placental trophoblasts at 10 days of gestation. A high proportion of iNKT cells was also detected in the decidua at the site of attachment of the placenta. The CD1 molecule is not actively involved in the regulation of early development of embryo till the blastocyst stage, and the true biological role of CD1 in preimplantation development remains to be determined. However, it may play a role in the placenta and in embryo development during midgestation by preventing lysis of fetal and placental cells through an interaction with decidual iNKT cells at the feto-maternal interface