Granulocyte precursors are the principal cells in bone marrow that stimulate allospecific cytolytic T-lymphocyte responses.

Mouse bone marrow cells were fractionated and enriched for functional activity as stimulators of allospecific cytolytic T-lymphocyte (CTL) responses in vitro. The relevant stimulator cells were enriched sequentially in the low-density fraction of bone marrow, its 2-hr adherent and 18-hr non-adherent fractions and in the FcR-negative fraction of 18-hr non-adherent cells. The functionally enriched cell population contained over 90% granulocyte precursors by ultrastructural analysis. The results indicate that granulocyte precursors are the principal cells in bone marrow that stimulate alloreactive T-cell responses.