Abstract
Abstract: :
Purpose: In C57BL/6 (B6) mice, interactions between CD4+ T (Th1) type T cells and Langerhans cells (LC), including B7/CD28 costimulation, are critical in the host response resulting in corneal perforation after infection with Pseudomonas aeruginosa (P. aeruginosa) (Hazlett et al., J. Immunol. 2001;166:1292). Other studies (Barrett et al., IOVS (Suppl.) 2003;716:29) have shown that surgical removal of cervical lymph nodes (CLN) before corneal infection with the bacteria had no significant effect on subsequent T cell trafficking into and cell activation in the cornea. The purpose of the current study was twofold: 1) to confirm that CLN are not required for T cell trafficking into cornea using an animal model that lacks peripheral (cervical) lymph node development; and 2) to determine if T cell activation is specific or nonspecific for P. aeruginosa antigen. Methods:Immunostaining for CD4 and CD25 was used to examine T cells in the cornea of infected B6.129S2–Ltatm 1 Dch (B6 Ltα–/–) vs. wt B6 mice. In addition, BALB/c–TgN (DO11.10)10LoH (OVA specific) mice that posses a MHC class II restricted rearranged T cell receptor transgene and react specifically to ovalbumin were tested. Before infection, the cornea of these vs. wt BALB/c mice was scarified and sterile beads topically applied to attract LC (and subsequently CD4+, CD25+ T cells after infection–Hazlett et al., IOVS 2001;43:189). Eyes from transgenic and wt mice were enucleated at 5 and 7 days post infection (p.i.), and frozen sections were cut and immunostained with rat anti–mouse mAbs KJ1–26 (DO11.10), CD4 and CD25 (IL–2 receptor). Results: Positive immunostaining for CD4 and CD25 T cell markers was detected in the cornea of B6 Ltα–/– mice and appeared similar to the cellular infiltrate detected in the cornea of wt B6 mice. KJ–126 positive T cells were detected in the transgenic mouse cornea at 5 and 7 days p.i. When dual staining was used, KJ–126 positive cells (ova specific) failed to stain with CD25, and did not express dual labeling, indicating that they were not activated. In contrast, CD4+, CD25+ T cells were detected in the cornea of infected wt BALB/c mice, as reported before. Conclusions: These data suggest: 1) that draining submaxillary and/or superficial CLN are not required for subsequent T cell trafficking into the cornea after infection with P. aeruginosa; 2) that T cells enter the cornea after infection from adjacent conjunctival and/or other vessels; and 3) that T cells are specifically activated in situ in cornea by bacterial antigen.
Keywords: Pseudomonas • antigen presentation/processing • bacterial disease