Cytokine responses in patients with pneumonia caused by Chlamydia or Mycoplasma

The serum concentrations of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) were measured by enzyme immunoassays in 44 patients with Chlamydia (n = 13) or Mycoplasma (n = 14) pneumonia or influenza A infection (n = 17) and in 20 control subjects. The levels of IFN-gamma were raised in 29/44 patients. The concentrations of IL-6 were raised in 32/44 patients. Raised levels of TNF-alpha were seen in 26/44 but there was no significant difference between the levels of the different groups of patients. All three cytokines indicated clinical recovery when acute and convalescent samples from 10 patients with Chlamydia pneumonia were analyzed. IFN-gamma, IL6 and TNF-alpha are present in the circulation in the majority of patients with Chlamydia and Mycoplasma pneumonia and in influenza A infection. We suggest that repeated measurement of cytokines, such as IL-6, IFN-gamma and TNF-alpha, may be useful in the management of lower respiratory tract infections but further studies are needed to define the value of cytokine measurements in acute pneumonia.