Granulocyte function disorders: aspects of development, genetics and management

Factors influencing predisposition to sepsis in children with cancers and acquired immunodeficiencies unrelated to human immunodeficiency virus infection

OBJECTIVES

The main objectives of this review are to provide insight into the various factors that affect the risk of sepsis in immunocompromised children and to discuss special issues that should be considered when such patients are enrolled in clinical trials.

STRATEGY

A literature review was conducted, and authoritative references were consulted when appropriate. This was supported by discussion among experts at an international consensus conference on pediatric sepsis.

OUTCOME

The review discusses general issues as they relate to the factors that are associated with a predisposition to sepsis in children with cancers and non-human immunodeficiency virus (HIV)-related acquired immunodeficiencies. The host defects that are associated with specific infections are discussed, and an overview of the indicators of immune dysfunction in the previously well child is presented. Selected examples of patients with non-HIV-related acquired immunodeficiencies, including those with cancer or who have undergone solid-organ or hematopoietic stem-cell transplants are discussed. Special challenges that may affect clinical trials include the altered immune response as this relates to the definition of infection and disease and the assessment of outcomes and the heterogeneity of study populations due to the variable manifestations of immune deficiency states.

SUMMARY

Knowledge of the factors that are associated with sepsis in immunocompromised patients is important when such patients are to be entered into clinical trials on sepsis. These factors do not necessarily operate in isolation and may occur concurrently or sequentially. With these considerations in mind, clinical trials involving immunocompromised children can go forward and will very likely lead to significant advances in the care of this understudied population.

Hematopoietic chimerism and central tolerance created by peripheral-tolerance induction without myeloablative conditioning

Allogeneic hematopoietic chimerism leading to central tolerance has significant therapeutic potential. Realization of that potential has been impeded by the need for myeloablative conditioning of the host and development of graft-versus-host disease (GVHD). To surmount these impediments, we have adapted a costimulation blockade-based protocol developed for solid organ transplantation for use in stem cell transplantation. The protocol combines donor-specific transfusion (DST) with anti-CD154 mAb. When applied to stem cell transplantation, administration of DST, anti-CD154 mAb, and allogeneic bone marrow leads to hematopoietic chimerism and central tolerance with no myeloablation and no GVHD. Tolerance in this system results from deletion of both peripheral host alloreactive CD8+ T cells and nascent intrathymic alloreactive CD8+ T cells. In the absence of large numbers of host alloreactive CD8+ T cells, the transfusion that precedes transplantation need not be of donor origin, suggesting that both allospecific and non-allospecific mechanisms regulate engraftment. Agents that interfere with peripheral transplantation tolerance impair establishment of chimerism. We conclude that robust allogeneic hematopoietic chimerism and central tolerance can be established in the absence of host myeloablative conditioning using a peripheral transplantation tolerance protocol.