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 regulate d or critically dependent on T-cell help, it is not surprising that ma ny studies have also shown a variety of defects in humoral immunity af ter thermal injury. However, the nature of the relationship between th e in vitro ability to produce antibody and subsequent in vivo response s 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. Se rum anti-TT titers and the numbers of anti-TT secreting splenocytes we re determined. Results. Splenocytes from burned animals displayed norm al 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 I gG antibody production. Conversely serum titers of TT-specific IgG ant ibody were persistently lower in burn, compared with sham groups. Chan ges in serum immunoglobulin levels did not account for this marked dis crepancy between enhanced in vitro IgG plaque formation but impaired i n vivo level of TT antibody. Conclusions. The data suggest that therma l injury is associated with a diminished ability to propagate and main tain a normal IgG antibody response, despite the presence of normal or increased numbers of antigen-specific B cells.