Fyn regulates eosinophil infiltration into the conjunctiva by downregulating the Th2 response.
OBJECTIVE
Under certain circumstances, fyn may serve to negatively regulate the differentiation of naïve helper T (Th) cells into Th2 cells. This study aimed to investigate whether fyn negatively regulates the development of experimental immune-mediated blepharoconjunctivitis (EC), in which Th2 cells play an important role in C57BL/6 mice.


METHODS
C57BL/6 background wild-type (WT) or fyn knockout (fyn-/-) mice were subcutaneously immunized with ragweed (RW) adsorbed in aluminum hydroxide. Ten days later the mice were challenged with RW in eye drops, and 24 h after challenge, eyes, blood and spleens were harvested for histology, measurement of serum IgE, and proliferation or cytokine assays, respectively. RW-primed splenocytes from WT and fyn-/- mice were cultured in the presence of RW. Seventy-two hours later, either whole splenocytes or isolated CD4+T cells were transferred into syngeneic WT mice. Four days after the transfer, the recipient mice were challenged with RW and evaluated as described above.


RESULTS
Infiltration of eosinophils into the conjunctiva induced by active immunization was significantly increased in fyn-/- mice relative to WT mice. Total serum IgE was also significantly higher in fyn-/- mice than in WT mice. In parallel, a higher level of IL-4 production from splenocytes was induced by concanavalin A stimulation in fyn-/- mice than in WT mice. In contrast to active immunization, transfer of whole splenocytes or separated CD4+T cells derived from WT or fyn-/- mice induced similar levels of eosinophilic infiltration in WT mice.


CONCLUSIONS
Fyn regulates infiltration of eosinophils into the conjunctiva through downregulation of Th2 responses. This negative regulation is exerted only during the induction phase of EC.
Fukushima
Atsuki
A
Department of Ophthalmology, Kochi Medical School, Kochi University, Kohasu, Oko-cho, Nankoku, 783-8505, Japan. fukusima@med.kochi-u.ac.jp
Yamaguchi
Tomoko
T
Ozaki
Akemi
A
Taniguchi
Taketoshi
T
Udaka
Keiko
K
Ueno
Hisayuki
H
D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D003228:Conjunctiva / Q000473:pathology*; D003233:Conjunctivitis, Allergic / Q000188:drug therapy / Q000276:immunology* / Q000473:pathology; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000502:physiology*; D004804:Eosinophils / Q000473:pathology*; D005260:Female; D007073:Immunoglobulin E / Q000276:immunology; D015847:Interleukin-4 / Q000378:metabolism; D015848:Interleukin-5 / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D051076:Proto-Oncogene Proteins c-fyn / Q000494:pharmacology*; D013154:Spleen / Q000473:pathology; D018418:Th2 Cells / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism
D015848:Interleukin-5; D015847:Interleukin-4; D007073:Immunoglobulin E; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn