T-CELL RECONSTITUTION AFTER BONE-MARROW TRANSPLANTATION INTO ADULT PATIENTS DOES NOT RESEMBLE T-CELL DEVELOPMENT IN EARLY-LIFE

Immune reconstitution after marrow transplantation has some characteri stics of immune development in early life. Here we provide phenotypic data suggesting this may not be true for T cells (particularly CD4(+) T cells) in the case of marrow transplantation into adults, T cells fr om 35 adult patients at 1 year after transplant, 14 normal neonates an d 22 normal adults were studied by 3-color flow cytometry. Marked disp arity between the phenotype of neonatal vs post-transplant T cells was found, Of the total CD4(+) T cells, the neonates had supranormal perc entages of CD45RA(high), L-selectin(+), CD29(low/-), CD11a(low/-) and CD28(+) cells whereas most patients at 1 year after transplant had sub normal percentages of these CD4(+) T cell subpopulations. (sub/supra-n ormal denotes below/above normal adult values), Absolute blood counts of naive (CD45RA(high), L-selectin(+), CD29(low/-) and CD11a(low/-)) C D4(+) T cells correlated inversely with patient age, Neonates had also supranormal percentages of CD45RA(high), L-selectin(+), CD29(low/-), CD11a(low/-) and CD28(+) CD8(+) T cells whereas the patients (particul arly those with chronic GVHD) tended to have subnormal percentages of these CD8(+) T cell subpopulations. Contrary to the CD4(+) T cells, th ere was no correlation between the absolute counts of CD45RA(high), L- selectin(+), CD29(low/-) or CD11a(low/-) CD8(+) T cells and patient ag e. Whereas the vast majority of neonatal T cells were CD38(high), most patient and normal adult T cells were CD38(-) or CD38(intermediate) ( both CD4(+) and CD8(+) T cells), We conclude that, in contrast to earl y life, the production of naive CD4(+) T cells is deficient in adult ( and particularly elderly) transplant recipients.