Parasite Immunology zyxwvu 1980, zyxwv 2, 1-10 zyxwvu Trypanosoma cruzi: binding of parasite antigens to mammalian cell membranes R.RIBEIR0 DOS SANTOS zyxw & L.HUDSON Department of’parasitology, University zyxw of Sao Paulo, 14100 Ribeiro Preto, Suo Paulo, Brasil and Department of Immunology, St George’s Hospital Medical School, London Accepted for publication 2 August 1979 Summary Muscle and neuronal cell lines were infected with Trypunosoma cruzi and stained for the presence of parasite antigens by immunofluorescence. Up to 72 h post infection, fluorescence was limited to the intracellular amastigote stages. After the release of parasites, at about 96 h, fluorescence was also associated with the membranes of normal and infected cells. This finding was reproduced by passive sensitization of uninfected cells using amastigote antigens at protein concentrations as low as 10 pg ml-I. Intriguingly, although both normal and transformed cells of muscle and nervous tissue origin adsorbed significant quanti- ties of antigen, lymphocytes and erythrocytes failed to show any detectible uptake. Keywords: Trypanusoma cruzi, parasite antigens Introduction It has long been known that a host may modify the surface of a parasite, either directly or indirectly, by biochemical and immunological means. This interfer- ence may take the form of an active immune response leading to loss of membrane integrity and eventual death of the parasite, but more subtly, the host may trigger a sequential expression of parasite genes producing a series of antigenic shifts in surface components (Cross 1975). In the extreme case, host antigens may adsorb to protozoan (Dwyer 1976) or metazoan (Smithers 1976) parasite surfaces pro- ducing host-like membrane characteristics. The situation in which parasite antigens may modify the membranes of host cells is of great significance when one considers disease pathogenesis. In some circumstances this may serve as a protective mechanism by which the host could potentially eliminate intracellular parasites, such as viruses (Zinkernagel & Correspondence: L.Hudson, Dept of Immunology, St George’s Hospital Medical School, London SW zyxwvutsr 17 ORE 0141-9838/80/0300-000l$02.00 zyxwvu 0 1980 Blackwell Scientific Publications 1