RSV is an important cause of lower respiratory tract illness in infants and the elderly worldwide. The components involved in immunity and those that contribute to inflammation of RSV-induced disease are not clearly understood. To address the relationship between activation antigen and cytokine expression, intracellular levels of IL-2, IL-4, IL-5 and IFN-gamma were determined for CD3, CD44, CD49d, CD54, CD62L and CD102 lymphocytes from the bronchoalveolar lavage and spleen. To examine activation at the DNA level, lymphocytes expressing IL-2, IL-4, IL-5 or IFN-gamma were analysed for G2+M DNA content or phosphatidylserine expression (apoptosis). Trafficking of lymphocytes to the BAL was detected at day 5 p.i., peaked day 7 p.i., and predominately involved CD54(+)and CD102(+)lymphocytes expressing high levels of IL-2, IL-4, IL-5 and IFN-gamma. Lymphocytes expressing CD44(+), CD49d(+)and CD62L(lo)were also observed, however they expressed these cytokines to a lesser extent. DNA analysis of lymphocytes expressing IL-2 or IFN-gamma revealed higher G2'M levels compared to lymphocytes expressing IL-4 or IL-5, suggesting greater activation of Th(1)-type lymphocytes in the lung. These data demonstrate that RSV-induced pulmonary inflammation involves extensive cellular activation and cytokine expression, particularly by CD54(+)and CD102(+)lymphocytes in the lung.
Copyright 2000 Academic Press.