Translocation of Thy-1 antigen and a fluorescent lipid probe during lymphoblastoid cell interaction with Mycoplasma hyorhinis

The translocation of membrane-associated components during in vitro surface interactions between BW5147 murine T-lymphoblastoid cells and Mycoplasma hyorhinis was investigated. Thy-1 antigen (shown to be selectively associated with mycoplasmas following their detachment from infected BW5147 cells) was found by immunoferritin techniques to be localized at the surface of organisms colonizing lymphoblastoid cells. These results are consistent with a transfer of Thy-1 to membranes of mycoplasmas on the lymphoid cell surface. The exchange of membrane lipid-associated components was further investigated with the fluorescent lipid probe 1,6-diphenyl-1,3,5-hexatriene (DPH). Fluorescence polarization of DPH was much less pronounced in uninfected BW5147 cells than in mycoplasmas--a result indicating markedly different probe environments. The increase of fluorescence intensity and the characteristic polarization in mycoplasmal supernatant fractions obtained after incubation of organisms with DPH-labeled BW5147 cells indicated translocation of DPH from lymphoid cells to mycoplasmas. Incorporation of the probe into mycoplasmas using supernatants from DPH-labeled BW5147 cells (incubated alone) was not demonstrated; this observation is consistent with, but does not prove, a contact-dependent process of exchange. Direct monitoring of the exchange of surface antigens and lipophilic probes may be useful in studying the interaction of hydrophobic surface glycoproteins with membranes and the role of membrane components in mycoplasma-host cell interactions.