Uterine dendritic cells (DCs) are critical for activating the T cell response mediating maternal immune tolerance of the semiallogeneicfetus. GM-CSF (CSF2), a known regulator of DCs, is synthesized by uterine epithelial cells during induction of tolerance in early pregnancy. To investigate the role of GM-CSF in regulating uterine DCs and macrophages, Csf2-null mutant and wild-type mice were evaluated at estrus, and in the periconceptual and peri-implantation periods. Immunohistochemistry showed no effect of GM-CSF deficiency on numbers of uterine CD11c+ cells and F4/80+ macrophages at estrus or on days 0.5 and 3.5 postcoitum, but MHC class II+ and class A scavenger receptor+ cells were fewer. Flow cytometry revealed reduced CD80 and CD86 expression by uterine CD11c+ cells and reduced MHC class II in both CD11c+ and F4/80+ cells from GM-CSF–deficient mice. CD80 and CD86 were induced in Csf2−/− uterine CD11c+ cells by culture with GM-CSF. Substantially reduced ability to activate both CD4+ and CD8+ T cells in vivo was evident after delivery of OVA Ag by mating with Act-mOVA males or transcervical administration of OVA peptides. This study shows that GM-CSF regulates the efficiency with which uterine DCs and macrophages activate T cells, and it is essential for optimal MHC class II- and class I-mediated indirect presentation of reproductive Ags. Insufficient GM-CSF may impair generation of T cell-mediated immune tolerance at the outset of pregnancy and may contribute to the altered DC profile and dysregulated T cell tolerance evident in infertility, miscarriage, and preeclampsia.

The dendritic cells and related antigen-presenting cells (APCs) that activate lymphocytes for acquired immunity in the female reproductive tract are not well characterized. The aim of the present study was to examine heterogeneity among uterine APCs in mice and, specifically, to determine whether phenotypically and functionally distinct subpopulations of dendritic cells and macrophages can be identified. Using immunohistochemistry, abundant cells expressing APC-restricted molecules major histocompatibility complex (MHC) class II, F4/80, class A scavenger receptor, macrosialin, and sialoadhesin were evident in estrous mice. Cells expressing the costimulatory molecule B7-2 were rarely observed. Flow cytometric analysis revealed three subpopulations of uterine APCs. Undifferentiated macrophages were F4/80-positive (+), MHC class II-negative (-) cells, of which 70-80% expressed CD11b, but few expressed class A scavenger receptor, macrosialin, or sialoadhesin. Mature macrophages were F4/80+/MHC class II+ cells, of which approximately 50% expressed CD11b, class A scavenger receptor, macrosialin, and sialoadhesin. Uterine dendritic cells were F4/ 80-/MHC class II+ cells, with stimulatory immunoaccessory function relative to uterine macrophages and heterogeneous expression of dendritic markers 33D1, DEC205, CD11c, and CD1. Experiments in ovariectomized mice showed that undifferentiated macrophages were steroid hormone dependent but that mature macrophages and dendritic cells persisted after depletion of ovarian steroid hormones, although with altered phenotypes. In summary, our findings identify three discrete populations of APCs inhabiting the murine uterus and suggest that both mature macrophages and dendritic cells differentiate from undifferentiated macrophage precursor cells. Plasticity in the ontogenetic and functional relationships between uterine dendritic cells and macrophages likely is critical in regulating immune responses conducive to reproductive success.

Immune responses directed at glycosylphosphatidylinositol (GPI) anchors of Plasmodium falciparum may offer protection against symptomatic malaria. To independently explore the effect of age on generation of the anti-GPI IgG response, we measured serum anti-GPI IgGs in a longitudinal cohort of migrant Javanese children (6-12 years old) and adults (Ն20 years old) with equivalent numbers of exposures to P. falciparum in Papua, Indonesia. While the peak response in adults was achieved after a single infection, comparable responses in children required Ն3-4 infections. Significantly fewer children (16%) than adults (41%) showed a high (optical density > 0.44) anti-GPI IgG response (odds ratio [OR] ‫ס‬ 3.8, 95% confidence interval [CI] ‫ס‬ 2.3-6.3, P < 0.0001), and adults were more likely to show a persistently high response (OR ‫ס‬ 5.5, 95% CI ‫ס‬ 1.0-56.8, P ‫ס‬ 0.03). However, the minority of children showing a strong response were significantly less likely to experience symptoms with subsequent parasitemia compared with those with a weak response (OR ‫ס‬ 4.0, 95% CI ‫ס‬ 1.1-13.8, P ‫ס‬ 0.02). This effect was not seen among high-and low-responding adults (OR ‫ס‬ 1.2, 95% CI ‫ס‬ 0.5-2.8, P ‫ס‬ 0.60). Host age, independent of cumulative exposure, apparently represents a key determinant of the quantitative and qualitative nature of the IgG response to P. falciparum GPI.

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