Current topic: the role of macrophages in the uterine response to pregnancy.

Immunohistological experiments have established patterns of distribution of macrophages in the pregnant uterus and some data have been accumulated on potential chemoattractants for these cells. The results of several lines of inquiry indicate that, as with macrophages in other tissues, these cells are multi-functional. Further experimentation is likely to be technically demanding because of indications that intricate hormone-prostaglandin-cytokine networks regulate uterine macrophage activities. The question of cytokine synthesis by uterine macrophages is particularly intriguing (Hunt, 1989a, Journal of Reproductive Immunology, 16, 1-17) and particularly difficult. These morphologically heterogenous cells are interspersed throughout the uterus with other types of cells that synthesize some of the same molecules, and the manipulations required for isolation could easily affect transient gene transcription (Taniguchi, 1988). Thus, many experiments must be performed on intact tissues using immunohistology and in situ hybridization. Although these remarkable cells undoubtedly contribute to the required developmental events of pregnancy, uterine macrophages may have detrimental as well as beneficial effects, particularly in cases of infection. Activation by interferons and bacterial lipopolysaccharides (LPS) disrupts normal synthetic patterns, and results in secretion of increased concentrations of bioactive proteins and lipids. Higher levels of IL-1 (Romero et al, 1989), TNF-alpha (Casey et al, 1989) and IL-6 (Romero et al, 1990), as well as increased levels of prostaglandins (Romero et al, 1987), all products of activated macrophages, are associated with pregnancy termination due to infection. Some of these molecules could induce premature labour, and others might alter cellular functions.(ABSTRACT TRUNCATED AT 250 WORDS)