Analysis of leukocytes recruited to the pancreas by diabetogenic T cell clones

To investigate host leukocytes recruited to the pancreas by diabetogenic T cells, we administered islet-specific CD4⁺ T cell clones to 2-week-old nonobese diabetic (NOD) mice and examined the resulting pancreatic infiltrate by flow cytometry. Two different Vβ4⁺CD4⁺ T cell clones, BDC 2.5 and BDC 6.9, were found to recruit a heterogeneous T cell population as determined by staining with a panel of anti-TCR Vβ monoclonal antibodies. The majority of the diabetes-initiating, Vβ4⁺ T cell clones migrated to the spleen whereas only 5-8% of the T cell population infiltrating the pancreas was Vβ4⁺. Anti-IL-2 receptor staining indicated that fewer than 10% of the total population of infiltrating lymphocytes within the pancreas were in a highly activated state. We have further found that normal splenic T cells from the NOD mouse proliferate poorly to IL-2 in vitro, yet secrete IFN-γ in response to IL-2 stimulation. These results suggest that the recruited host T cells in our disease transfer system are not directly pathogenic but, rather, are responding to the small numbers of inflammatory T cell clones by providing cytokines that facilitate the disease process.