Steel factor (c-kit ligand) stimulates the in vitro growth of immature CD3-/CD4-/CD8- thymocytes: synergy with IL-7.
The ability of Steel factor (SLF) to stimulate the growth of immature thymocytes alone and in combination with IL-7 was assessed. In suspension cultures of CD4-/CD8- thymocytes, SLF itself did not induce significant proliferation, but in combination with IL-7, it induced a greater response than did IL-7 alone. In fetal thymus lobe submersion cultures, SLF stimulated the growth of cells to a magnitude similar to that of IL-7 and the combination resulted in a synergistic response. Phenotypic analysis of these cells revealed that SLF in comparison to IL-7 stimulated the growth of a less mature population. The synergistic growth stimulated by the combination of IL-7 and SLF occurred in a population of IL-2R+/CD4-/CD8-/CD3- cells. Cells grown in SLF expressed low levels of IL-2R and overnight culture in IL-7 dramatically increased IL-2R expression. Thus, these results are consistent with the hypothesis that SLF stimulates the growth of a less mature thymocyte population than does IL-7.
Morrissey
P J
PJ
Department of Immunology, Immunex Corporation, Seattle, Washington 98101.
McKenna
H
H
Widmer
M B
MB
Braddy
S
S
Voice
R
R
Charrier
K
K
Williams
D E
DE
Watson
J D
JD
D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D005260:Female; D005434:Flow Cytometry; D016298:Hematopoietic Cell Growth Factors / Q000502:physiology*; D016130:Immunophenotyping; D015851:Interleukin-7 / Q000502:physiology*; D008213:Lymphocyte Activation / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009924:Organ Culture Techniques; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D016176:T-Lymphocyte Subsets / Q000166:cytology*; D013950:Thymus Gland / Q000166:cytology*
D015703:Antigens, CD; D016298:Hematopoietic Cell Growth Factors; D015851:Interleukin-7; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins; D019089:Stem Cell Factor