Recovery of mononuclear cell subsets after bone marrow transplantation: overabundance of CD4+CD8+ dual-positive T cells reminiscent of ontogeny.

Patients after bone marrow transplantation are immunodeficient for months to years. To understand better the pathogenesis of this immunodeficiency, we studied quantitative reconstitution of blood monocytes, natural killer (NK) cells, T cells, and B cells at 2-22 months post-transplant. The results indicate monocyte and NK counts generally recover within 2 months, followed by CD4-CD8+ T cell, B cell, and finally (after > 1 year) CD4+CD8- T cell numbers. Dual-positive CD4+CD8+ T cells (which were barely detectable in normal adults), CD4-CD8+ T cells and B cells transiently reached supranormal levels during recovery. Both CD4+CD8- and CD4-CD8+ T cells were larger than controls throughout the 2-year follow up. Comparison with neonatal and infant mononuclear cell subsets suggested the reconstitution of CD4+CD8+ T cells and B cells is similar to ontogeny. In contrast, the reconstitution of CD4+CD8- T cells did not resemble ontogeny.