Naive and memory T cells migrate in comparable numbers through the normal rat lung - Only effector T cells accumulate and proliferate in the lamina propria of the bronchi

T tells reach the lung via the pulmonary and bronchial arteries that supply the alveolar and bronchial regions. Although these regions are differentia lly affected by T cell-mediated diseases, the migration of T-cell subsets i n these two regions has not been studied. Naive, memory, and effector T cel ls were injected into congenic rats and traced in sections of normal lung. All three T-cell subsets were found in large numbers in the alveolar region and exited again quickly. Only effector T cells accumulated in the lamina propria of the bronchi, Further, 72 h after injection 6% of the effector T cells still proliferated in the lung, whereas apoptotic effector T cells we re only observed 1 h after injection (0.2%). Thus, not only effector and me mory but also naive T tells continuously migrated through the lung. The pre ferential accumulation of effector T cells in the bronchial lamina propria may explain why some diseases preferentially affect the bronchial region.