AbstractHost defense mechanisms are cell‐ mediated, humoral and phagocytic. Acquired derangements of one or many of the immune antibacterial defenses are common after injury. These defects include (a) a failure of T‐ cell response (DTH) to antigen stimulation manifested by negative skin test reactions to common antigens (anergy); (b) a failure of humoral response, or B‐ cell depression after appropriate antigen stimulation; and (c) development of serum inhibitors of phagocyte chemotaxis.Anergy reflects an immunodeficiency state more profound than impaired T‐ cell function alone and, if left uncorrected, is associated with a markedly increased incidence of sepsis and associated mortality. Therapeutic implications of these findings for now and the future are summarized.