THE HUMORAL IMMUNE-RESPONSE AFTER THERMAL-INJURY - AN EXPERIMENTAL-MODEL

Background. Severe thermal injury is associated with major alterations in cell-mediated immunity. Because most B-cell responses are regulated or critically dependent on T-cell help, it is not surprising that many studies have also shown a variety of defects in humoral immunity after thermal injury. However, the nature of the relationship between the in vitro ability to produce antibody and subsequent in vivo responses remains unclear. Methods. With a murine model of thermal injury, the primary and secondary humoral immune response to tetanus toxoid (TT) was examined during a 6-week period after shan burn or burn injury. Serum anti-TT titers and the numbers of anti-TT secreting splenocytes were determined. Results. Splenocytes from burned animals displayed normal or decreased TT-specific immunoglobulin (Ig)M plaque formation. In contrast, however, IgG plaque formation was persistently increased for up to 6 weeks after thermal injury, suggesting a switch from IgM to IgG antibody production. Conversely serum titers of TT-specific IgG antibody were persistently lower in burn, compared with sham groups. Changes in serum immunoglobulin levels did not account for this marked discrepancy between enhanced in vitro IgG plaque formation but impaired in vivo level of TT antibody. Conclusions. The data suggest that thermal injury is associated with a diminished ability to propagate and maintain a normal IgG antibody response, despite the presence of normal or increased numbers of antigen-specific B cells.