Strain specific production of a negative regulator of IL-3 (NIL-3): difference in the negative feedback mechanism of hemopoiesis among mouse strains.

The producing cells of the negative regulator of interleukin-3 (NIL-3) were investigated. The 5-fluorouracil-treated bone marrow cells did not produce NIL-3. The bone marrow cells of stem cell-depleted W/WV mouse did not produce the NIL-3, either. The production of NIL-3 was different among mouse strains. Mice of C3H/HeN, A/J and ICR strains produced NIL-3, but the C57BL/6 mice did not produce NIL-3. These results indicate that the negative feedback mechanism of hemopoiesis is different among mouse strains. In the present study, we could not definitely identify the NIL-3 producing cells, although the present results are suggestive that the stem cells in cycle are a NIL-3 producer. Instead, we found that hemopoietic regulatory mechanisms might be different among mouse strains, especially in C57BL/6 mice.