[Evaluation of conventional and new generation tests for testing the humeral response to Mycoplasma pneumoniae antigens in natural infections in humans. II. Occurrence and level of mycoplasma antibodies in patients with respiratory tract infections].

The aim of the study was to observe the frequency of occurrence of mycoplasmal antibodies detected by the complement fixation test (CFT), immunoelectroprecipitation test (IEPT) and ELISA in selected groups of patients with respiratory tract infections and to determine the dependence of these antibodies on the age of patients and length of illness. 521 serum samples collected from 404 persons were examined; 378 samples were obtained from 276 patients with pneumonia and 143 from 128 patients with upper respiratory tract infections. Additionally, serum samples from 50 patients with B. pertussis were investigated in this section of the study as a control test to demonstrate the specificity of the tests. It was established that in patients with pneumonia mycoplasmal antibodies are, as a rule, detected in much higher titers than in patients with upper respiratory tract infections. On with age, the level of mycoplasmal antibodies detected in all the three tests rose in the examined patients. In the highest titers antibodies against M. pneumoniae were detected in adults within the age 21-50. As a rule mycoplasmal IgM antibodies reached a level 2-3 times higher than IgG antibodies. It was also shown that already during the first week of illness antibodies against M. pneumoniae determined by the CFT, IEPT and ELISA in the sera of the examined persons are higher than the level known to be diagnostically significant. During the second week of illness IgA and IgM antibodies have a particularly high titer while the growth of titer of IgG antibodies is relatively small. A very high level of IgM, along with progressive growth of IgG antibodies and the related gradual decrease of the index value IgM/IgG, was observed in the serum of patients up to the 4th week of illness. In some cases, in titer known to be diagnostically significant, this high level was present even many months after the appearance of disease symptoms. Antibodies against M. pneumoniae in class of immunoglobulin A disappeared the fastest. Thus it is believed that demonstrating their characteristics dynamics or detecting these antibodies in the patient's serum in the titer assumed to be diagnostically significant can indicate an acute stage of illness.