Cell-cell interaction in human granulopoiesis: Role of T lymphocytes

T lymphocytes have been implicated in the pathogenesis of granulocytopenias. We studied the effects of unstimulated and pokeweed mitogen (PWM) activated intact (Ti) and partially purified T cell subpopulations (Tγ and Tnonγ, i.e., Tμ plus T(0)) on in vitro granulocyte-macrophage colony formation (CFU(GM)) by autologous normal human bone marrow (BM). Coculture of BM with Ti, Tγ, or Tnonγ caused only a slight decrease in the numbers of colonies and clusters; however, when cultured with a mixture of Tγ and Tnonγ, the inhibition was significant. In contrast, activation of T cells or T cell subsets with PWM resulted in a marked decrease in colony formation. These results demonstrate that: 1) PWM-activated T cells or its subpopulations will inhibit autologous BM colony formation in vitro. The suppression seen with admixes of unstimulated Tγ and Tnonγ is presumptive evidence that prior cell-cell interaction(s) may be required for the generation of inhibitory cells in this system; and 2) this model may represent an in vitro counterpart of immune-mediated cytopenias in man.