ISOTYPE-SPECIFIC ANTIBODY-RESPONSES TO ACUTE MYCOPLASMA-PNEUMONIAE INFECTION

Background: Mycoplasma pneumoniae-induced respiratory infections affec t millions of patients and have been implicated in exacerbation of bro nchial asthma. IgE may be involved in such exacerbations. While specif ic IgG and IgM responses to Mycoplasma pneumoniae are well described, the response of other isotypes is less known. Purpose: To determine wh ether specific IgE and what subclasses of IgG are formed in response t o Mycoplasma pneumoniae infection. Methods: We studied 20 patients wit h acute Mycoplasma pneumoniae infection, in whom the diagnosis was con firmed by a 16-fold increase in complement fixation titer between acut e and convalescent serum samples. We developed an enzyme-linked immuno sorbent assay (ELISA) for the determination of IgG, IgA, and IgM antib odies specific for Mycoplasma pneumoniae protein antigens. We used Wes tern blotting to confirm the results of the ELISA and to detect Mycopl asma-specific IgG subclasses and IgE. Results: Changes in Mycoplasma p neumoniae-specific IgG, IgA, and IgM were significant. Western blots o f Mycoplasma pneumoniae antigens in 13 convalescent sera showed specif ic IgG in all, IgM in 11, IgA in 6, and IgE in 10. The IgG response co nsisted mainly of IgG1 and IgG3, and to a lesser degree of IgG2 and Ig G4. Conclusions: We conclude that Mycoplasma pneumoniae infection is a ssociated with a significant specific IgA and IgE response, in additio n to the well-known responses of IgG and IgM. As IgE is involved in al lergic reactions, the production of Mycoplasma pneumoniae-specific IgE may have a role in exacerbation of bronchial asthma.