- Email: [email protected]
Cell surfaces and their phenotypes in early mammalian development
local effects to divert maternal im~nunity. Chemical analysis of trophoblast has revealed several antigens which exert a physiological barrier effect. One of these is a non-allotypic glycoprotein whose distribution on normal tissues is limited to trophoblast. Antiserum mounted to this trophoblast antigen (TA) is called anti-TAl, and it inhibits allogeneic responses as measured by the mixed-lymphocyte-culture (MLC) reactions. The TAI antigen itself is also capable of inhibiting MLC reactions, and this has been attributed to a paralysis of T-cells. Another group of TA is allotypic with broad tissue distribution including lymphocytes. This group is called TA2 and it contains the trophoblast lymphocyte cross reactive (TLX) antigens. Anti-TLX sera have defined three antigens, compatibility for which between mating couples is associated with recurrent spontaneous abortions. An hypothesis has been advanced that TA2 and TAI collaborate as a hapten-carrier system to stimulate blocking antibodies that function at the trophoblast's surface to form a type of barrier to maternal immune cells. The barrier concept has thus changed from anatomical to physiological, and now it appears to be immunological.
CELL SURFACES AND THEIR PHENOTYPES IN EARLY MAMMALIAN DEVELOPMENT MICHAEL EDIDIN The Johns Hopkins University Baltimore, MD 21218 USA The appearance and function of particular gene products in cell surface membranes depends upon the expression of the genes specifying the products, upon the correct processing of the primary gene products, and upon the physical state of the membranes in which these products are inserted. For example, expression of membrane glycoproteins is contingent upon correct glycosylation by ~lycosyl transferases, upon the details of lipid composition and organisation in the membrane bilayer, and upon associations between membrane integral proteins and the cell cytoskeleton. In this lecture I will emphasise the ways in which the physical properties of membrane lipids and the mobility of membrane components affect membrane phenotypes. Examples will be drawn from embryonic development and from some model cell culture systems. The effects of lipid composition on local lipid fluidity and upon organisation of bilayer lipids into domains will be shown to affect both enzyme function and surface antigen display. The role of lateral diffusion in organising and differentiating cell surfaces will be analysed. We will see that the large size of cells in the early embryo makes diffusion in the plane of the membrane an important factor in creating differentiated regions of the cell surface.
NATURAL AND ARTIFICIAL CHIMERAS AND REPRODUCTIVE IMMUNOLOGY RUPERT E. BILLINGHAM, D.Sc. Department of Cell Biology; The University of Texas Health Science Center at Dallas; 5323 Harry Hines Boulevard; Dallas, Texas 75235; U.S.A. Chimeras are organisms of composite make-up, comprising cells, tissues or organs of two or more zygote lineages. They may result from experimental or therapeutic transplantation, e.g., of a kidney, or a transfusion of blood or other cells, or from natural processes such as the exchange of cells between mother and fetus across the placenta, or between fetuses as a consequence of a common placental circulation, as in th~ case of cattle, marmosets and rarely
CELL SURFACES AND THEIR PHENOTYPES IN EARLY MAMMALIAN DEVELOPMENT MICHAEL EDIDIN The Johns Hopkins University Baltimore, MD 21218 USA The appearance and function of particular gene products in cell surface membranes depends upon the expression of the genes specifying the products, upon the correct processing of the primary gene products, and upon the physical state of the membranes in which these products are inserted. For example, expression of membrane glycoproteins is contingent upon correct glycosylation by ~lycosyl transferases, upon the details of lipid composition and organisation in the membrane bilayer, and upon associations between membrane integral proteins and the cell cytoskeleton. In this lecture I will emphasise the ways in which the physical properties of membrane lipids and the mobility of membrane components affect membrane phenotypes. Examples will be drawn from embryonic development and from some model cell culture systems. The effects of lipid composition on local lipid fluidity and upon organisation of bilayer lipids into domains will be shown to affect both enzyme function and surface antigen display. The role of lateral diffusion in organising and differentiating cell surfaces will be analysed. We will see that the large size of cells in the early embryo makes diffusion in the plane of the membrane an important factor in creating differentiated regions of the cell surface.
NATURAL AND ARTIFICIAL CHIMERAS AND REPRODUCTIVE IMMUNOLOGY RUPERT E. BILLINGHAM, D.Sc. Department of Cell Biology; The University of Texas Health Science Center at Dallas; 5323 Harry Hines Boulevard; Dallas, Texas 75235; U.S.A. Chimeras are organisms of composite make-up, comprising cells, tissues or organs of two or more zygote lineages. They may result from experimental or therapeutic transplantation, e.g., of a kidney, or a transfusion of blood or other cells, or from natural processes such as the exchange of cells between mother and fetus across the placenta, or between fetuses as a consequence of a common placental circulation, as in th~ case of cattle, marmosets and rarely