Selective lysis of early embryonic cells by the alternative pathway of complement--a possible mechanism for...

Early embryonic cells and early mouse embryos were shown to activate the alternative pathway of complement, and to be highly sensitive to complement-mediated cytolysis (Kircheis et al, In Vivo 9: 85-98, 1995). Under further development embryonic cells become resistant. The induction of resistance to the alternative pathway of complement correlates with: a) altered splicing of Cr2-transcript and b) changes in the acidic glycolipids under differentiation. Early embryonic cells have low amounts of sialic acid-containing glycolipids or express mainly GM3. The induction of differentiation changes the glycolipid pattern leading to an increase in membrane-bound sialic acid. The importance of membrane-bound sialic acid in the restriction of complement activation is demonstrated by increased sensitivity to complement after pre-treatment of cells with neuraminidase. The results indicate that there is target-specific lysis of early embryonic cells by the alternative pathway of complement. Early embryonic cells activate the alternative pathway of complement by expressing activators and low levels of membrane-bound sialic acid. Induction of differentiation changes the glycolipid pattern, leading to an increase in membrane-bound sialic acid sufficient to restrict complement-activation on the cell surface.