IL-17F/IL-17R interaction stimulates granulopoiesis in mice.
OBJECTIVE
IL-17F, a member of the interleukin (IL)-17 cytokine family, most closely resembles IL-17A structurally. IL-17A is a potent stimulator of granulopoiesis; its expression is induced in response to microbial challenge. Although IL-17F is considered to be a weak IL-17A analog that is also mediating its effect via IL-17R, its exact role and in vivo functions are unknown. Our goal was to determine the in vivo activity of IL-17F on granulopoiesis as well as on release of granulopoiesis-stimulating downstream cytokines in mice and directly compare its effect to IL-17A.


METHODS
Murine IL-17A (mIL-17A) or IL-17F (mIL-17F) was expressed in vivo in C57BL6 mice using adenoviral gene transfer technology. Peripheral cell counts were assessed as well as hematopoietic precursors using colony-forming assays at set time points. Downstream cytokines were measured using enzyme-linked immunosorbent assay and reverse transcriptase polymerase chain reaction.


RESULTS
We found mIL-17F to have similar expression kinetics as mIL-17A in splenocytes in vitro and in vivo, following challenge with microbial agents. Overexpression of mIL-17F in vivo resulted in similar neutrophilia and only in slightly reduced myeloid progenitor expansion when compared to mIL-17A. In vivo, there was no difference in releases for granulocyte-macrophage colony-stimulating factor; regulated on activation, normal T expressed and secreted; interferon-inducible protein-10; IL-6; and monocyte chemotactic protein-1 between either cytokine. IL-1A, macrophage inflammatory protein -2 (MIP), KC, and granulocyte colony-stimulating factor expression was approximately half of that seen with mIL-17A.


CONCLUSIONS
Both IL-17A and IL-17F are induced by similar stimuli, have similar expression kinetics and despite only minimal in vitro activity for IL-17F, surprisingly they exert similar in vivo bioactivity. IL-17F bioactivity appears to be augmented in vivo through mechanisms that require further investigation.
Tan
Weihong
W
Department of Gynecology, The People's Hospital of Guangxi Province, P. R. of China.
Huang
Weitao
W
Gu
Xiaogang
X
Zhong
Qiu
Q
Liu
Bainan
B
Schwarzenberger
Paul
P
D000818:Animals; D016207:Cytokines / Q000096:biosynthesis / Q000097:blood; D006098:Granulocytes / Q000502:physiology*; D006410:Hematopoiesis; D020381:Interleukin-17 / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000502:physiology; D053722:Receptors, Interleukin-17 / Q000502:physiology*
D016207:Cytokines; D020381:Interleukin-17; D053722:Receptors, Interleukin-17