The possible immunological bases of recurrent spontaneous abortion (RSA) are still largely unknown, aberrant type 1 cytokine production: interferon-y (IFNy), and a defective type 2 cytokine: Interleukk-10 (IL-10) has been suggested to be related to the incidence of unexplained RSA, therefore, the present sfudy was conducted to investigate the possible role of the cytokines: IFN-y and IL-10 in the pathology of RSA. their role in inducing or inhibiting the expression of certain adhesion molecules; platelet endothelial cell adhesion molecule (PECAM)-l and vascular cell adhesion molecule (VCAM)-l. in addition to detecting the presence of human cytomegalovirus (HCMV) as an immune modulator affecting the expression of such cytokines in those patients. The study included 24 pregnant women with RSA (group A), and 12 women had at least three previous normal pregnancies and presented with abortion for the first time including two women, with elective pregnancy termination, taken as comparison group (group B). all of them were in the first trimester of pregnancy. History.. was taken from each patient with her previous medical records and investigations: and paraffin embedded blocks of the curate samples trom each case were retrieved. These samples were investigated for the expression for IFN-y and IL-10 by in situ hybridization technique using biotinylated DNA probes of IFN-y and IL-10 respectively. While the expression of PECAM-1, VCAM-1. von Willebrand factor (vWF) and HCMV proteins was detected by immunohistochemistry using specific monoclonal antibodies for these markers. The results of the in situ hybridization analysis revealed a significant increase in the level of IFN-y in situ expression in the RSA group compared to that of the first abortion group (p<0.001). While on the contrary, the reverse was detected when the level of IL-10 in situ expression was in question, since, the the current data revealed a significant increase in the level of IL-10 in si fit expression among women with first abortion compared to those with RSA (p<0.001). However, each of the two investigated cytokines revealed a similar pattern of expression in both the decidua and trophoblasts. In addition, although the current study could not document a significant correlation between IFN-y and IL-10 in situ expression whether among RSA or first abortion groups (r= -0.047, p>0.05; r=0.133, p>0.05 respectively), however, an interesting observation was revealed in that IFN-y/IL-10 ratio among the first-group was approximately three times higher than that of the later group with a statistically significant difference of p < 0.001. The second core of the current study was designed to investigate the possible role of PEC AM-1 and VCAM-1 in the pathology of RSA. Based on immunohistochemical analysis, exclusively, there was a significant increase in the surface expression of VCAM-1 in women with RSA weighted against that of the control group (p<0.001). Whether VCAM-1 or PECAAM-1 surface expression was modulated by any of the two investigated cytokines, the current -study revealed that exclusively, there was a significant correlation between IFN-y in situ expression and immunohistochemical detection of VCAM-1 on endothelial cells (r =0.419, p< O.05) in patients with RSA. The third core of this study investigated the possible role of HCMV infection in the pathology of RSA, in which the Chi-square analysis revealed no significant association between the immunohistochemical detection of HCMV early protein and recurrent pregnancy loss, in addition to the lack of significant difference in the level of IFN-y or IL-10 in situ expressions between HCMV protein positive and negative cases (p >0.05) indicating that HCMV infection as manifested by the presence of viral early protein might not have a significant role in the pathology of RSA. In conclusion, the data of this study strengthen the possibility that type-1 immune response may have the upper hand in the pathology of RSA on multidirectional bases including the surface expression of adhesion molecules, since these molecules enhance the inflammatory process in the endothelial lining of decidual blood vessels.