The Role of the Spleen in Radiation Injury. *

Summary and Conclusions

These hematologic and histologic data indicate that:

1) Severe anemia, leucopenia, and thrombocytopenia develop in mice after a single dose of 600 r whole-body X radiation.

2) Ectopic erythrocytopoiesis, in the lead-protected spleens of mice given 600 r whole-body X radiation (exclusive of spleens) compensates with such rapidity and so extensively for the destruction and interruption of this activity in the marrow spaces that no anemia of significance becomes apparent. Ectopic granulocytopoiesis and megakaryocytopoiesis in the lead-protected spleens compensates significantly but at a slower pace and less completely for the bone marrow destruction.

3) A marked and sustained decrease in the amount of lymphatic tissue is produced in the lead-protected spleens of animals given 600 r whole-body X radiation. This decrease in lymphatic tissue may perhaps be a result of (a) unsuccessful competition of the lymphatic tissue with the ectopic hematopoiesis for nutritional requirements, (b) actual indirect effect of radiation and (c) a differential humoral suppression from some unknown site.

The rapidity with which erythrocytopoiesis transfers from the X-ray damaged bone marrow to the lead-protected spleen in the absence of anemia suggests that the mechanism of stimulation of erythrocytopoiesis under the conditions of this experiment may involve some factor or factors other than, or in addition to, the accepted hemoglobin-oxygen relationship.

This technic permits more or less exclusive protection of the spleen or the appendix or other visceral tissues from irradiation while applying various dosages to the remainder of the body. It provides a method of studying potential sites and mechanism of the production of ectopic blood formation, possible secondary effects of radiation as well as offering possibilities for determining the potential role of such sites in immune reactions, in preventing or alleviating radiation-induced hemorrhagic phenomena and in the study of survival or recovery from radiation injury.