Macrophage heterogeneity in human fetal tissue. Fetal macrophages

Abstract

SUMMARYThe immunophenotype of the macrophage population in human fetal tissue was studied, using a panel of monoclonal antibodies against cells of the macrophage/monocyte lineage. Using a doublelabelling technique two main populations were observed in tissue from 14 weeks of estimated gestational age (EGA); EBMl 1 ' DR* and EBMl 1 ' DR cells of which a small proportion were also RFD7'. Most macrophages were negative with 3.9, an antibody specilic for the adhesion molecule P150.95 and LP9 which is specific for a lysosomal enzyme. The exception to this was a small population of positive cells in the thymus. Small numbers of 3.9* cells were also infrequently observed In tissue at and above 17 weeks of EGA. while occasional RFD9' cells were only observed in most tissues, before this time. The higher percentage of macrophages were DR' DQ DP , with a few DQ* eells appearing at 15 weeks of EGA. In the thymus. DQ' cells outnumbered DP* cells especially in the medulla. These results indicate the heterogeneous and Immature nature ofthe fetal macrophage population and point to the importance of age. tissue-specific factors and probable immune mediators in macrophage differentiation.

Development of immune organs and functioning in humans and test animals: Implications for immune intervention studies

“…Organized mucosal lymphoid tissues, like the Peyer's patches in the small intestines are already grossly visible in human early in the third (late) trimester, at a time that the anlage of mouse Peyer's patches is just apparent. Nevertheless Peyer's patches, colonized by lymphocytes, were present (soon after) birth in the 4 species, which supports the notion that MALT is important in the establishment of a functional immune system in all 4 species [38,70]. Germinal centers were found postnatally in all 4 species; adult morphology being present in the juvenile period in minipig, rat and mouse (adult morphology has not been scored in human).…”

“…Prenatal. The thymus anlage is already present in the early gestational period, with the most critical period of growth between 7 and 14 weeks of gestation [36][37][38][39]. CD7+ T cells gradually colonize the anlage, and the thymus cortex and medulla become distinguishable.…”