Recombinant murine IL-3 fails to stimulate T or B lymphopoiesis in vivo, but enhances immune responses to T cell-dependent antigens.
We have explored the in vivo effect of IL-3 on the lymphopoiesis and humoral responses of mice bearing osmotic minipumps loaded with murine rIL-3 for 1 to 4 wk. A marked splenomegaly due to the accumulation of hemopoietic precursors was seen, but no increase was found in the lymphoid organs in the total number of cells belonging to the T or B lymphocyte lineage, i.e., of L3T4+ or Lyt-2+, or of allospecific cytotoxic T lymphocyte precursor for the T lineage, or of sIg+ or B220+ cells, or of B colony-forming cells for the B lineage; total activity of natural killer and lymphokine-activated killer cells was decreased. In contrast to the splenomegaly, a marked diminution in the number of thymocytes was observed, suggesting that rIL-3 in large amounts does suppress the T lymphopoiesis, perhaps as the result of the selective stimulation of early progenitor cells toward the hemopoietic pathway. rIL-3 perfusion during immunization increased the IgM and IgG responses to a T cell-dependent antigen, human IgG, and prevented tolerance induction by the deaggregated human IgG, although in the same conditions it did not modify the response to a T cell-independent antigen. Our results suggest that in vivo IL-3 does not act directly on lymphocytes or their precursors, but may potentiate the humoral immune response to T cell-dependent antigens, presumably by acting on accessory cells.
Kimoto
M
M
Department of Pathology, University of Geneva, Centre Medical Universitaire, Switzerland.
Kindler
V
V
Higaki
M
M
Ody
C
C
Izui
S
S
Vassalli
P
P
D000818:Animals; D000941:Antigens / Q000276:immunology*; D001402:B-Lymphocytes / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D005260:Female; D006410:Hematopoiesis / Q000187:drug effects*; D007377:Interleukin-3 / Q000494:pharmacology*; D008221:Lymphoid Tissue / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D011994:Recombinant Proteins / Q000494:pharmacology; D013163:Splenomegaly; D013601:T-Lymphocytes / Q000187:drug effects
D000941:Antigens; D007377:Interleukin-3; D011994:Recombinant Proteins