Abnormal primary antibody responses in pediatric trauma patients

Lymphocyte function in wound healing and following injury

BACKGROUND

Injury activates a cascade of local and systemic immune responses.

METHODS

A literature review was undertaken of lymphocyte function in wound healing and following injury.

RESULTS

Lymphocytes are not required for the initiation of wound healing, but an intact cellular immune response is essential for a normal outcome of tissue repair. Injury affects lymphocyte immune mechanisms leading to generalized immunosuppression which, in turn, increases host susceptibility to infection and sepsis. Although the exact origin of post-traumatic immunosuppression remains unknown, stress hormones and immunosuppressive factors, such as inflammatory cytokines, prostaglandin E2 and nitric oxide, affect lymphocyte function adversely. Post-traumatic impairment of T lymphocyte immune function is reflected in decreased lymphocyte numbers, as well as altered T cell phenotype and activity. Antibody-producing B lymphocytes are variably affected by injury, probably secondary to alterations of T lymphocyte function, as a result of their close interaction with helper T cells. Therapeutic modulation of the host immune response may include non-specific and specific interventions to improve overall defence mechanisms.

CONCLUSION

Early resuscitation to restore lymphocyte function after injury is important for tissue repair and the prevention of immunosuppression.

Human intravenous immunoglobulin in primary and secondary antibody deficiencies

IVIG is of value in patients with primary and secondary antibody deficiencies. High dose IVIG therapy is usually the treatment of choice for patients with primary antibody deficiency disease. Sufficient IVIG should be given to maintain IgG trough levels of > 500 mg/dl; this usually requires a dose of 400 to 500 mg/kg/month. Adverse side effects to IVIG has been described; the two most common serious side effects are hepatitis C and aseptic meningitis. New procedures to inactivate hepatitis C (and other viruses) are now in place. Aseptic meningitis is usually associated with high IVIG doses given rapidly to patients with autoimmune and inflammatory disease; its cause is not known. Subcutaneous infusions of IG or IVIG at weekly intervals has been shown to be clinically efficacious, well-tolerated and a less expensive alternative to monthly IVIG infusions. IVIG has been used with encouraging results in selected pediatric patients with HIV infection. The benefit is primarily in patients with CD4 counts > 200 cells/mm2 who receive no P. carinii pneumonia prophylaxis. IVIG may also be of value in preventing or ameliorating infection in other secondary antibody deficiencies including patients with malignancies; patients with protein-losing enteropathy and nephrotic syndrome; severely ill care patients with shock, trauma or surgery; premature infants and patients undergoing transplantation procedures; and severely burned patients. Guidelines for selecting patients for IVIG are offered.

Distribution of human herpesvirus 6 and varicella-zoster virus in organs of a fatal case with exanthem subitum and varicella

The distribution of human herpesvirus 6 (HHV-6) and varicella-zoster virus (VZV) was examined in autopsy samples from a fatal case with both virus infections. A 9-month-old boy developed convulsive seizures followed by macular skin rashes, rapidly progressed to brain death, and died 15 days after the onset, when signs of varicella were noted. An isolation of HHV-6 from blood and evaluation of antibody activities to various viral agents including HHV-6 were performed before his death. Postmortem examinations included: (i) isolation of HHV-6 and VZV from tissues or organs; (ii) detection of both virus antigens in tissues or organs by an indirect immunofluorescent assay using monoclonal antibodies to both viruses; (iii) amplification of both viruses and human herpesvirus 7 DNA sequences by a nested polymerase chain reaction assay; and (iv) endonuclease digestion of amplified products of HHV-6 DNA for differentation of variants A and B. Human herpesvirus 6 DNA was detected in peripheral blood mononuclear cells (PBMC) and plasma obtained at the eruptive stage but present only in PBMC 15 days after, indicating the primary infection with HHV-6, although the virus was not isolated from the same blood sample and a significant rise in the antibody titers to HHV-6 was not observed. Both virus antigens and DNA were detected in various tissues or organs obtained at autopsy, but only VZV was isolated from these samples, suggesting disseminated infection with both viruses in an infant. All the amplified products of HHV-6 DNA were variant B. Among the findings for the distribution of virus antigens, it was noteworthy that HHV-6 antigen was demonstrated in the endothelial cells of small vessels in the frontal lobe of the brain. There was no evidence of HHV-7 infection. These data indicate that the primary HHV-6 infection closely followed by the primary VZV infection had the potential hazard of an unexpected and apparently life-threatening event, in which disseminated infections with both viruses were noted in multiple tissues or organs including the brain.

Immunoglobulins and IgG subclasses in children following severe head injury

OBJECTIVE

To study immunoglobulin production after severe blunt head trauma in children.

DESIGN

Serum for IgG, IgM, IgA, IgE, and IgG subclasses were drawn from 10 children admitted with severe head injury (ISS 31.2, GCS 5.4) on day 1, 7, 14 and 21 after injury.

RESULTS

5 of the 10 patients developed infection between 7 and 14 days and 2 died of complications of pneumonia. On day 1, IgM levels averaged 95.6% of the mean of the age-specific normal controls. By day 7, IgM levels averaged 383% (p < 0.01). While all patients were within the age-specific normal range (+/- 2 SD) on day 1, 7 of 10 patients were above the normal range by day 7. There was no difference in IgM levels between infected and non-infected patients. Five patients were below the age-specific normal range for IgG on day 1, with 3 still low on day 7. By day 21, IgG levels averaged 141% of the mean of the age-specific normal controls. IgG subclasses followed a pattern similar to total IgG levels. Marked increases in IgE were seen in 3 patients.

CONCLUSIONS

IgM levels increased dramatically in all patients within seven days of the injury. While 50% of these children had a deficit of IgG in the first week, total IgG and IgA levels increased after injury, but not as rapidly as IgM levels. Unlike pediatric burn patients, there is no persistent hypogammaglobulinemia following severe blunt trauma in children.

Safety and efficacy of intravenous immunoglobulin prophylaxis in pediatric head trauma patients: a double-blind controlled trial

Infection is one of the major complications of severe head trauma in children. To assess whether intravenous immunoglobulin (IVIg) decreases the incidence of secondary infection after head injury in children, a randomized, double-blind trial was performed. Thirty-three children (mean age, 6.67 years; mean injury severity score, 32.8; mean Glasgow coma score, 6.1) with severe head injuries were enrolled; 1 child was excluded, 18 received IVIg, and 14 received the placebo preparation. Four hundred milligrams per kilogram of IVIg or albumin placebo was administered within 48 hours of admission. IgG levels were obtained before the infusion and then 1 week later. Patients were monitored for evidence of infection for the next 21 days. There was a 66% increase in mean IgG levels in the treatment group compared with 45% in the control group (P = .057). One death occurred in the IVIg group and two in the placebo group. No significant differences in the incidence of pneumonia, sepsis, presumed sepsis, or any other type of infection was noted. There was no difference in the number of days on mechanical ventilation or in number of hospital days. There were no side effects. It is concluded that prophylactic administration of commercial IVIg at a dose of 400 mg/kg, although safe, had no effect on the incidence of secondary infections in children with severe head injuries.

Immunosuppression in Trauma Patients

An immunosuppressed state develops following traumatic injury, which makes patients more prone to develop infection. A variety of disturbances accompany injury that affect both specific and nonspecific components of host defense. Many clinical studies have attempted to evaluate the many deficits that follow injury and place the patient at a higher risk for infection. Several components of host defense are affected simultaneously and include (1) cellular changes (decreased activation of T-lymphocyte subsets with decreased helper cells, increased suppressor T-cell function, increased but abnormal activity of macrophages, activation of polymorphonuclear leukocytes with depressed chemotaxis and killing); (2) depressed nonspecific and specific serum immunity (e.g., depressed fibronectin and immunoglobulin levels); (3) the presence of altered cytokine levels (interleukin-1 [IL-1], IL-2, IL-6, tumor necrosis factor) levels; (4) ongoing serum proteolytic activity; and (5) the generation of serum suppressive peptides. An in-depth understanding of the deficits that occur following injury in host defense will provide the basis for therapeutic intervention.

Association of autoimmunity with IgG2 and IgG4 subclass deficiency in a growth hormone-deficient child

An association between humoral immune deficiency and childhood autoimmune disease has been previously established. We describe a 7-year-old male with severe autoimmune disease, recurrent infections, a marked deficiency of IgG2 and IgG4, and an inability to respond to polysaccharide antigens. This child was also found to have isolated growth hormone (GH) deficiency. Laboratory results included a positive anti-smooth muscle antibody, a positive Raji-cell assay for immune complexes, and normal levels of IgG, IgM, and IgA. IgG subclasses revealed an IgG1 of 1225 (normal for age, 280-1120 mg/dl), IgG2 of less than 10 (30-630 mg/dl), IgG3 of 36 (40-250 mg/dl), and IgG4 of less than 4 (11-620 mg/dl). No increase in antibody titer was noted to either Pneumovax or unconjugated Haemophilus influenzae vaccine. Numbers of circulating B cells (CD19) were markedly diminished (less than 0.5%). Liver biopsies have shown chronic active hepatitis. Somatomedin C was 0.28 U/ml (normal for age, 0.5-2.06 U/ml). Challenge with either L-dopa or clonidine produced a peak GH response of 2.3 ng/ml (normals = greater than 7 ng/ml). Children with autoimmune disorders should be evaluated for IgG subclass deficiencies and ability to make antibody in response to antigen challenge regardless of the serum immunoglobulin levels. Growth failure in immune-deficient children should not be assumed to be due to chronic illness or recurrent infections. Other etiologies for growth failure should be sought.