The research objective of this doctoral thesis was to examine the expression of the cytotoxic molecule of granulysin at the level of protein and messenger ribonucleic acid (mRNA) at the interface of maternal and embryonic tissues in anembryonic pregnancy and missed abortion, and to compare the results with decidual tissue from an electively terminated normal first trimester pregnancy. Materials and methods: Basal decidua samples from a normal and an anembryonic pregnancy as well as a missed abortion were obtained from the Obstetrics and Gynecology Clinic of the Clinical Hospital Center Rijeka Of immunoassays, we used immunohistochemical staining of antigens in decidual tissue embedded in paraffin (cytokeratin, granulysin, IL-15, Apaf-1, NF-B, CD56) with computer quantification of the number of stained cells/mm2 of tissue and semiquantitative analysis of the intensity of staining (H score). We performed multiple immunofluorescence labelling of cytokeratin and CD56, IL-15, granulysin, Apaf-1 or in decidual tissue with fluorescent microscope reading, as well as the staining of CD3/CD56 and NKp46, NKp44, CD94, NKG2A or NKG2D in the suspension of DMCs obtained by enzymatic degradation using flow cytometry. Using the real-time polymerase chain reaction method (RT-qPCR), we determined the gene expression for granulysin and perforin. Results: The content of CD3-CD56⁺ NK cells in the DMC suspension, the absolute number of CD56⁺ cells and IL-15⁺ cells/mm2 of decidual tissue was lower in the missed abortion. The frequency of NKG2A, NKG2D and NKp46 markers on CD3ˉCD56⁺ NK cells in the DMC suspension from the missed abortion was statistically significantly lower than in the normal pregnancy. In anembryonic pregnancy proportion of NK cells did not change. The frequency of NKG2C, CD94 and NKP44 did not differ significantly. The messenger RNA for granulysin was four times lower in the DMC from the missed abortion, and four times higher in the DMC from the anembryonic pregnancy, while the mRNA for perforin was increased in both. In the normal pregnancy, cytoplasmic staining of granulysin was predominant, while, in the pathological pregnancies, granulysin was present in cell nuclei. The absolute number of NF-B⁺ cells/mm2 of decidual tissue was the highest in the anembryonic pregnancy. The lowest frequency of NF-B⁺ cells was determined in the trophoblast villi of the missed abortion. Conclusion: A less efficient killing of trophoblasts with granulysin may be involved in a slower rejection of trophoblasts in anembryonic pregnancy and missed abortion, because of a decreased supply of granulysin to trophoblast nuclei compared to normal pregnancy.