Answer:
Infection remains the major cause of death in burn patients. Destruction of the mechanical barrier of the skin contributes to susceptibility, but alterations in immune function may be critical as well - both humoral and cellular. The cellular immune response is depressed, demonstrated by the prolonged survival of skin allografts. With burns of 20% or more, impairment in cellular immunity is proportional to the size of the burn. During the 1st week, total lymphocyte numbers are decreased, there is inversion of the normal T-suppressor to T-helper ratio which normalizes by the second week in recovering patients. An increase in monocytes, granulocytes, and B-lymphocytes occurs by postburn day 1, but IgG levels are decreased and gradually return to normal levels by day 14-28. IL-2 production is impaired and is directly correlated with burn size. PMN's exhibit reduction in chemotactic activity and impaired phagocytosis. Serum from burn patients demonstrates immunosuppressive factors - a suppressive peptide inhibits neutrophil chemotaxis. Other factors in burn serum include complement degradation products which inhibit phagocyte function, immunoglobulin fragments, prostaglandins and endotoxin.