Abstract
Purpose: :
The leukocyte response is a fundamental component of the body’s defense in response to infection. We utilized the transparency of the cornea to obtain images of CD8 lymphocytes and bone marrow derived cells responding to Listeria infection of the iris.
Methods: :
Listeria monocytogenes (2 ul with 5000 cfu/ul) was directly placed adjacent to the mouse iris using a glass capillary needle. Ampicillin therapy prevented rapid spread of infection. Imaging of the immune response serially was performed with indirect immunofluorescent microscopy and facilitated by the use of fluorescent bacteria and/or transgenic mice whose CD8 T cells recognize Listeria or transgenic mice whose neutrophils and monocytes fluoresce due to a GFP label on the promoter for lysozyme.
Results: :
Touching the needle tip to the iris resulted in a focal Listeria infection. Numerous lysozyme expressing cells rapidly accumulated at the site of infection and increased over the next 24 hours. CD8 positive cells also migrated to the site of infection but were less numerous than the neutrophils and monocytes. Time lapse imaging of CD8 migration suggested a complex, non-linear pathway similar to what we have previously observed with CD4 cells in the iris in response to antigen.
Conclusions: :
This is one of the first studies to image serially the leukocyte response to an infection in a living animal and the first to perform studies in the iris. CD8 migration in the iris in response to this infection appears similar to migration of CD4 cells which we have previously described. The ability to visualize cell migration in response to infection will help clarify the vital mechanisms that underline this essential function.
Keywords: microbial pathogenesis: experimental studies • inflammation • iris