Increased expression of activation markers and adhesion molecules on lung T-cells compared with blood in the normal rat

Lymphocytes play an important role in many lung diseases and are routinely accessible by bronchoalveolar lavage (BAL). Lymphocytes from the BAL (BAL p ool) have a different subset composition to those from peripheral blood, co nsisting mainly of activated T-cells. The aim of this study was to examine whether preferential migration of activated T-cells to the bronchoalveolar space or factors of the specific microenvironment mediate this phenomenon. The expression of adhesion molecules and cellular activation markers (inter cellular adhesion molecule-1, leukocyte function-associated antigen-1, CD2, CD44, interleukin-2 receptor and L-selectin) was studied on T- and B-cells not only in the BAL and peripheral blood (blood pool), but also in the com partments in between, such as the lung vascular perfusate (marginal pool) a nd the lung interstitium (interstitial pool), with the experiments being pe rformed simultaneously in the same animals. Low levels of adhesion molecule expression Here observed on T-cells in the blood and marginal pool, medium levels in the lung interstitium and the hig hest levels in the RAL. "Memory" (CD45R(low)) and "naive" (CD45(high)) T-ce lls in the lung compartments showed a higher expression of adhesion molecul es compared with blood. However, the predominating CD15R(low) T-cells showe d a significantly higher expression than the CD45R(high) cells, indicating that CD4+ CD45R(high) T-cells had changed their phenotype to CD45R(low). In conclusion, a high level of expression of leukocyte function associated antigen-1 and intracellular adhesion molecule-1 on the bronchoalveolar lava ge and interstitial T-cells is more likely to be the result of local, lung- specific induction than a prerequisite for migration into the bronchoalveol ar space.