TH1 AND TH2 CYTOKINE INDUCTION IN PULMONARY T-CELLS DURING INFECTION WITH RESPIRATORY SYNCYTIAL VIRUS

Helper T (Th) cells can be classified functionally into two main types , Broadly, Th1 cells play a major role in eliminating viral pathogens, while Th2 cells mediate anti-parasite immunity and allergic responses , These functions are thought to depend on characteristic and distinct patterns of cytokine production, Infection with human respiratory syn cytial virus, an important common cold virus, causes transient lymphoc ytic bronchiolitis in mice, Activated T cells are partly responsible f or this disease, but also eliminate the virus, To show whether polariz ed cytokine production occurs in individual cells during viral bronchi olitis, we sampled murine bronchoalveolar lavage and mediastinal lymph node cells before and after infection. RT-PCR of cellular mRNA and Ro w cytometric analysis of intracellular cytokine production showed a ra pid IFN-gamma response at both sites, which persisted for more than 3 weeks in the lung. Most IFN-gamma-producing cells were CD8(+), Some ea rly CD4(+) IFN-gamma-producing cells also made IL-10. Only low levels of IL-2, IL-4 and IL-5 mRNA or protein expression were detected at any time at either site, No cytokines were detected in B cell populations at either site, These novel techniques show the true complexity of cy tokine production patterns on a cell-by-cell basis, allowing T cells t o be reclassified according to function.