Development of T cell lineages in rat lacrimal glands

The purpose of this study was to examine T cell development in rat lacrimal glands, determine whether the thymus is the source of immature T cells in this tissue and compare lacrimal gland T lymphocytes with other T cell subpopulations.

Mononuclear cells were isolated from lacrimal glands of normal or thymectomized female Fischer 344 rats and stained for flow cytometric analysis.

The lacrimal gland T lymphocyte population included large percentages of cells with an activated phenotype and also subpopulations of immature, naive and memory T cells. The numbers of immature (Thy-1(+)) lacrimal gland T cells were unchanged following short-term adult thymectomy. In comparison, spleen had large percentages of naive T cells, only a small subpopulation of activated T cells, and similar percentages of immature (Thy-1(+)) T cells, which were nearly eliminated after thymectomy. Lacrimal gland T cells had small subpopulations of TCRgammadelta(+) and CD8alphaalpha( +) T cells, a large subpopulation of NKT cells and many integrin alphaEbeta7( +) T cells.

Lacrimal gland T cells are composed of a variety of subpopulations whose composition is distinct from splenocytes. The marked reduction of immature splenic T cell percentages eleven days after adult thymectomy indicates that these cells were mostly derived from thymic precursors. In contrast, the unchanged percentages of immature lacrimal gland T cells following thymectomy indicate that they may have an extrathymic source. These studies provide a foundation for further investigation into the cellular basis of lacrimal gland immunobiology.