Age and the immune response in pediatric renal transplantation.

Because renal transplant outcome is poorer in young children when compared with older children or adults, it is reasonable to question whether immune reactivity relative to renal allograft rejection differs between young children and adults. While this hypothesis is far from established, preliminary data suggest that young children may represent an immunologically-defined subgroup distinct from adults and perhaps at high risk for renal allograft rejection. From a histocompatibility standpoint, infants may show some subtle differences in HLA typing results when compared with older children or adults. Children may also be at higher risk than adults for rejection when the transplant is performed in the presence of a historically positive, currently-negative lymphocytotoxicity crossmatch. Several non-specific tests of cellular immunity have been used to characterize the strong immunologic responder, i.e. the person who has an increase tendency to vigorously reject a renal allograft. Children in general and young children in particular may fall into this group. Children 5 years old and younger have significantly increased numbers of CD2+, CD3+, and CD4+ T lymphocytes when compared with older children. Young children also have higher than expected functional indices of cellular immune function. Taken together, these data suggest that children, and particularly young children, may have a heightened immunologic responsiveness, which may in turn represent an increased propensity for allograft rejection. Appropriate modification in immunosuppression may be indicated to optimize renal transplant outcome.