| Abstract: | The cellular response to an intraperitoneal injection of antigen (tetanus toxoid) was studied in reconstituted animals in order to determine the mechanism of control of eosinophil granulocytopoiesis. Antigen treatment of the marrow cell donors did not consistently increase the number of spleen and bone marrow colonies in recipient animals or change the percentage of eosinophil or other hemopoietic colony types. Antigen pre-treatment of the irradiated recipients increased the percentage of eosinophil-containing colonies in the spleen and femoral bone marrow without significantly changing the total number of either spleen or marrow colonies. Antigen treatment of both the bone marrow cell donor and recipient produced a further increase in the percentage of eosinophil-containing colonies in the marrow cavity, but not in the spleen. Antigen treatment of the irradiated recipient increased the number of eosinophilic cells (but not the total number of cells) in both the peritoneal cavity and the bone marrow. Antigen treatment of both the marrow donor and recipient produced a further increase in the number of eosinophilic cells in the peritoneal cavity, but not in a single femur. Since antigen treatment of the marrow recipient, or recipient and donor, but not of the marrow donor alone, results in increased eosinophilic cell and colony numbers, the effect of antigen appears to be mediated through some host factor(s), perhaps the eosinophilic hemopoietic inducing microenvironment (HIM), rather than directly on the hemopoietic stem cells. |
