The corneas of naive mice contain both CD4+ and CD8+ T cells.

PURPOSE To determine if the corneas of naive mice contain resident CD4+ and CD8+ T cells. METHODS The presence of T cells in the corneas of naive BALB/c, C57BL/6, and SCID mice was determined by immunostaining with anti-CD4 (clone RM4-5) and anti-CD8 (clone 5H10-1) monoclonal antibodies. Immunostained corneal sections were examined by light microscopy, and immunostained intact corneas were examined by confocal microscopy. The levels of CD4 and CD8 mRNA transcripts in the corneas were determined by TaqMan reverse-transcriptase polymerase chain reaction (RT-PCR) analysis and compared with the expression of these transcripts in the corneas of HSV-1 infected mice. Finally, the number of CD4+ and CD8+ T cells in the cornea of BALB/c, C57BL/6, and ICR mice was determined by cell sorting. RESULTS Both light microscopic examination of corneal sections and confocal microscopic examination of intact corneas revealed the presence of CD4+ and CD8+ cells in the central and peripheral regions of the corneas of BALB/c and C57BL/6 mice. Stained cells were not detected in corneas of control SCID mice. CD4 and CD8 mRNA transcripts were detected in corneas of BALB/c and C57BL/6 mice while there were markedly lower levels of transcripts in SCID mice. The number of CD4 transcripts was lower than the number of CD8 transcripts in the corneas of both BALB/c and C57BL/6 mice. Finally, cell sorting showed the presence of both CD4+ and CD8+ T cells in corneas of BALB/c, C57BL/6, and ICR mice. CONCLUSIONS CD4+ and CD8+ T cells are present in corneas of naive C57BL/6, BALB/c, and ICR mice.