TGF beta 2 in rabbit blastocoelic fluid regulates CD4 membrane expression: possible role in the success of gestation

During pregnancy, major changes occur in the decidual cell population. One of these changes involves some phenotypical transformations of lymphocyte sub-populations. Since these variations might be due to the presence of the embryo, the current study was designed to investigate the implication of blastocoelic fluid (BF) in these changes and to determine the mechanism by which this phenomenon occurs.

Lymphocytes isolated from human peripheral blood (PBL) were cultured for 72 h in RPMI-FCS 10% and with or without BF day 12 (BF d-12) or Concanavalin A (ConA). After 72 h, T cells were labelled with anti-CD4 antibodies and Quantum Simply Cellular microbeads were used as a standard to evaluate the antibody binding capacity (ABC).

Treatment of human PBL with BF d-12 decreases the percentage of CD4 and TCR positive cells, as compared to non-stimulated cells, but has no significant effect on CD2, CD3, and CD8 positive cells. It was also demonstrated, for the first time, that transforming growth factor beta-2 (TGF beta 2) in BF day 12 diminishes the percentage of CD4 positive cells by downregulating CD4 membrane expression on leucocytes.

These findings suggest that the embryo plays a role in its own protection. Furthermore, it is predicted that any tissue producing TGF beta 2, such as certain types of tumor, downregulates the immune response, thus allowing tumor growth.