Further studies on the role of IL-12 in Pseudomonas aeruginosa corneal infection.
OBJECTIVE
Previous studies have shown that in Pseudomonas aeruginosa ocular infection, IL-12 drives a Th1 T-cell response and IFN-gamma production in susceptible (cornea perforates) C57BL/6 (B6) mice, and that after similar infection of resistant (cornea heals) BALB/c mice, no IL-12 is detectable in cornea at either the mRNA or protein levels. Therefore, the purpose of this study was to test whether BALB/c mice are capable of responding to exogenous IL-12 administration, and whether disease responsiveness following P. aeruginosa challenge is modified.


METHODS
Immunostaining, RT/PCR, recombinant cytokine injection, and histopathology were used. Statistical analysis was performed using an unpaired, two-tailed Student's t-test.


RESULTS
Injection of BALB/c mice with recombinant (r) IL-12 converted these normally resistant animals to the susceptible phenotype as evidenced by corneal perforation within 5-7 days after infection. RT-PCR analysis of the corneas of rIL-12 vs PBS/BSA-treated mice showed a significant increase in IFN-gamma and TNF-alpha mRNA levels in the rIL-12 vs PBS/BSA (vehicle)-treated mice at 3 and 5 days p.i. In addition, similar analysis of IL-4 mRNA levels showed decreased amounts of the cytokine in rIL-12 vs vehicle-treated mice. Injection of rIL-4 into susceptible B6 mice, however, failed to rescue these animals from corneal perforation following P. aeruginosa challenge.


CONCLUSIONS
These data provide evidence that BALB/c mice can respond to exogenous IL-12, that the cytokine promotes susceptibility by increasing IFN-gamma and TNF-alpha production, with a concomitant reduction in IL-4 levels; and that injected rIL-4 fails to rescue susceptible B6 mice from corneal perforation after bacterial challenge.
Hazlett
L D
LD
Department of Anatomy/Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA. lhazlett@med.wayne.edu
Huang
X
X
McClellan
S A
SA
Barrett
R P
RP
D000818:Animals; D003320:Corneal Ulcer / Q000276:immunology* / Q000473:pathology; D018450:Disease Progression; D015818:Eye Infections, Bacterial / Q000276:immunology* / Q000473:pathology; D005260:Female; D007124:Immunoenzyme Techniques; D018836:Inflammation Mediators / Q000378:metabolism; D007371:Interferon-gamma / Q000096:biosynthesis / Q000235:genetics; D018664:Interleukin-12 / Q000276:immunology* / Q000633:toxicity; D015847:Interleukin-4 / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008815:Mice, Inbred Strains; D011552:Pseudomonas Infections / Q000276:immunology* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000276:immunology / Q000633:toxicity; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012720:Severity of Illness Index; D018417:Th1 Cells / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics
D018836:Inflammation Mediators; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D018664:Interleukin-12; D015847:Interleukin-4; D007371:Interferon-gamma