Distribution of mosaicism in human placentae.

Traditional first trimester chorionic villus sampling (CVS) for prenatal diagnosis can be performed by cytogenetic analysis of cytotrophoblast or chorionic villous stroma. Approximately 2% of pregnancies studied by CVS show confined placental mosaicism (CPM) involving either cytotrophoblast, stroma or both. We present the results of a cytogenetic study of nine term placentae from pregnancies with prenatally diagnosed CPM. The aneuploid++ cell lines involved trisomies for chromosomes 7,9,16, and X. The cytotrophoblast and villous stroma from multiple biopsies of these placentae were examined using a combination of interphase and metaphase cytogenetic analysis. CPM was detected in all nine of the term placentae and both tissue-specific and site-specific patterns of mosaicism could be discerned. These results indicate that the analysis of villous stroma and cytotrophoblast from multiple placental biopsies is necessary to improve our understanding of the evolution of CPM during pregnancy and its effect on the fetus.

Epidermal Langerhans' cell induction of immunity against an ultraviolet-induced skin tumour.

Langerhans' cells (LC) have been shown experimentally to induce immune responses against many antigens; however, their role in the initiation of anti-tumour immunity has received little attention. This study examined the ability of murine epidermal LC to induce immunity to an ultraviolet radiation (UV)-induced skin tumour. Freshly prepared epidermal cells (EC) were cultured for 2 or 20 hr with granulocyte-macrophage colony-stimulating factor (GM-CSF), pulsed with an extract of the UV-13-1 tumour, then used to immunize naive syngeneic mice. Delayed type hypersensitivity (DTH) was elicited 10 days after immunization by injection of UV-13-1 tumour cells into the ear pinna, and measured 24 hr later. EC cultured with GM-CSF for 2 hr induced antitumour DTH, as did EC cultured for 20 hr without GM-CSF. Conversely, EC cultured for 2 hr without GM-CSF, or EC cultured for 20 hr with GM-CSF were unable to induce a DTH. Induction of immunity required active presentation of tumour antigens by Ia+ EC and was tumour specific. Thus Ia+ epidermal cells are capable of inducing anti-tumour immunity to UV-induced skin tumours, but only when they contact antigen in particular states of maturation.

Processing of complex antigens and simple hapten-like molecules by epidermal Langerhans cells.

Langerhans cells (LCs) are antigen-presenting cells of the skin that trap small contact-sensitizing molecules and induce cutaneous hypersensitivity. LCs can present larger molecules but the mechanisms of processing have required investigation. A system combining in vitro culture of antigen with epidermal cells in the presence of inhibitors, followed by fixation and transfer of these antigen/drug-treated epidermal cells to naive mice, was developed to investigate the steps of antigen processing. Langerhans cells undertake similar, but not identical, pathways for the processing of simple and complex molecules. Complex molecules such as trinitrophenyl conjugated to ovalbumin (TNP-OVA) were internalized and modification required a chloroquine-sensitive proteolysis step and a cycloheximide-sensitive protein synthesis step. This modified product was actively recycled to the cell membrane as presentation was inhibited by blocking receptor translocation with either monensin or cytochalasin B. Small contact sensitizers such as trinitrophenyl did not undergo modification but required internalization and presentation was also inhibited by blocking receptor translocation.

Characterization of an inversion duplication of the short arm of chromosome 8 by fluorescent in situ hybridization.

A de novo chromosome aberration in a woman with severe mental retardation and minor anomalies has been characterized cytogenetically. The patient's karyotype was described as 46, XX, inv dup (8)(p12-->p23.1). Previous Southern blot dosage studies with the marker locus D8S7 demonstrated that the patient was monosomic for this locus, suggesting that the rearrangement generated a duplication-deficiency chromosome. We have reinvestigated this patient using fluorescent in situ hybridization with chromosome 8 cosmids and an Alu-PCR product specific for 8p. These studies have confirmed directly that the duplicated chromosome also has undergone deletion.