Bacterial lipoteichoic acid sensitizes host cells for destruction by autologous complement

Lipoteichoic acids (LTA) released by gram-positive bacteria can spontaneously bind to mammalian cell surfaces. In the present study, erythrocytes (E) sensitized with pneumococcal LTA (LTA-E) were used as a model system to determine if LTA could render host cells susceptible to damage by autologous complement. Complement (C)-mediated lysis of LTA-E from normal rats and normal humans occurred when these cells were incubated in their respective autologous sera in vitro. In addition, when LTA-E from a C2-deficient human and from C4-deficient guinea pigs were incubated in their autologous sera, there was significant lysis in vitro, demonstrating a role for the alternative pathway. The in vivo survival of 51Cr-labeled autologous LTA-E was also studied. Only 2.9% of autologous LTA-E remained in the circulation of normal rats after 90 min. In contrast, 31.2% of autologous LTA-E remained in the circulation of rats depleted of C3. Intravascular hemolysis accounted for the clearance of LTA-E in the normal rats, whereas liver sequestration was responsible for clearance in the C3-depleted rats. These results demonstrate that LTA can render the host's cells susceptible to damage by its own complement system, establishing this as a possible mechanism of tissue damage in natural bacterial infections.