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 multifunctional. 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-α 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. Recent experiments in our laboratory suggest although trophoblast cells bear LPS receptors, damage to these cells during gram negative bacterial infections is more likely to result from encounters with macrophage-derived molecules than from exposure to LPS Hunt et al, 1989. Further experimentation in this area might lead to treatment regimens that would be effective in alleviating this major health problem. © 1990, Baillière Tindall. All rights reserved.