Expression of interleukin-11 during the human menstrual cycle: coincidencewith stromal cell decidualization and relationship to leukaemia inhibitoryfactor and prolactin

Interleukin-11 (IL-11) is crucial in the decidualization response of the ut erine stroma to the implanting blastocyst in the mouse. This study examined the localization and expression of IL-11 in human endometrium throughout t he menstrual cycle and of prolactin and leukaemia inhibitory factor (LIF) i n secretory phase endometrium. The mRNA expression of IL-11 receptor a and the signalling component, gp130, in endometrial tissue were also determined . Immunoreactive IL-11 was highest in the secretory phase and present in de cidualized stromal cells, glandular epithelial cells, endothelial and smoot h muscle cells, and the mRNA expression was verified by in-situ hybridizati on. Decidual cells showed the most intense staining. IL-11 receptor a and g p130 mRNA were detected throughout the cycle with minimal variation. Expres sion of IL-11 mRNA and protein preceded that of prolactin. While immunoreac tive prolactin was found in stromal, decidual and glandular epithelial cell s, prolactin mRNA was confined to decidual cells. In contrast, endometrial LIF expression preceded IL-11 but was largely confined to the glandular epi thelium. The sequence of appearance of LIF, IL-11 and prolactin suggests a synchronized role for each in the differentiation of the endometrium. The c yclical changes and cell type specific expression of IL-11 suggests a poten tial role in the decidualization of stromal cells.