CYTOKINE GENE-EXPRESSION IN IMMUNE MICE REINFECTED WITH MYCOPLASMA-PNEUMONIAE - THE ROLE OF T-CELL SUBSETS IN AGGRAVATING THE INFLAMMATORY RESPONSE

Cytokine gene expression was examined by qualitative and semiquantitat ive reverse transcriptase polymerase chain reaction (RT-PCR) in the lu ngs of Mycoplasma pneumoniae infected immune C57BL/6 mice depleted of either CD4(+), CD8(+) or both CD4(+) and CD8(+) T cells. Immediately a fter M. pneumoniae reinfection of control immune mice, mRNAs for TNF-a lpha, IFN-gamma, IL-1 beta, IL-6, IL-2 and IL-2 receptor were promptly detected in the lungs. In animals depleted of CD4(+) T cells, mRNA ex pression for IL-2, IL-2 receptor and IFN-gamma were completely abrogat ed and mRNA expression for TNF-alpha, IL-1 beta and IL-6 were reduced by 10- to 100-fold. In mice depleted of CD8(+) T cells, mRNA expressio n for IL-2 and the IL-2 receptor was also undetectable, while mRNA for TNF-alpha, IL-1 beta and IL-6 were only marginally decreased. Histolo gical evaluation of the infected lungs performed in parallel revealed dense mononuclear infiltrations around small bronchi and small blood v essels in control reinfected mice. In contrast, in CD4(+) T cell-deple ted mice, these focal accumulation of lung tissue infiltrating cells w ere found to be greatly reduced. The data indicate that the inflammato ry response in lung tissue thought to be mainly responsible for Mycopl asma pneumoniae disease is associated with an, increased level and a p rolonged expression of proinflammatory cytokines due to CD4(+) lung in filtrating T cells.