Identification of Immunological Biomarkers for Recurrent Pregnancy Loss

Background: Even though an immunology-based etiology underlying unexplained recurrent pregnancy loss (RPL) has been demonstrated, the exact molecular mechanisms are still poorly understood. Recently, we have identified for the first time RPL-associated proteins in blood of RPL patients using proteomic research tools. Among these proteins, PK-120 was weakly expressed at a molecular weight of 120 kDa, but was highly expressed at a modified molecular weight of 36 kDa in RPL patients. Interestingly, we detected a truncated form of PK-120 (36 kDa) in 67% RPL patients.

Objective: A previous study indicated that altered immunity in RPL is dominated by the Th1/Th2/Th17 and regulatory T cell paradigm. Here, the aim is to identify the role of two different fragments in RPL, and our findings suggest that it may be considered as a cause of pregnancy loss in humans.

Methods: Immunoprecipitation assay was performed to evaluate the full length PK-120 bound with Plasma Fletcher Factor. Immunocytochemistry (ICC) assay was used for detection and determination of the cellular translocalization of PK-120. Expression of Plasma Fletcher Factor resulted in stabilization of PK-120 in a dose dependent manner. Furthermore, to investigate the function of the two fragments, we performed enzyme-linked immunosorbent assays (ELISA) and cytokine meta-analysis, and cytokines were analyzed in the culture medium and serum samples.

Results: Expression of Plasma Fletcher Factor resulted in stabilization of PK-120 in a dose-dependent manner. The cytokines which were secreted from Th1 cells were higher in 36 kDa of PK-120-transfected cells, while Th2 and Th17-related cytokines were shown upregulated in the full-length of PK-120-transfected cells. These results were consistent with the data that showed in serum samples.

Conclusions: We suggest that a highly expressed PK-120 fragmented form as an acute phase protein may induce strong inflammatory response in pregnant women, resulting in failure of pregnancy maintenance.