Humoral and Cellular Immunity in Children withMycoplasma pneumoniaeInfection: a 1-Year Prospective Study

Abstract

To determine whether children have persistent abnormalities in cellular and humoral immunity development after acute Mycoplasma pneumoniae infection, serum immunoglobulin G (IgG), IgA, IgM, and IgE levels and lymphocyte phenotypes were determined. There were no changes in the levels of IgG, IgM, IgA, or CD4 ؉ or CD19؉ lymphocytes that were measured in M. pneumoniae-positive patients after 3 months or after 12 months, but there were increases in these in M. pneumoniae-negative patients. Serum IgE increased in M. pneumoniae-positive patients. We have shown alterations in immunity development after M. pneumoniae infection.Mycoplasma pneumoniae is a common pathogen of children's respiratory tracts (8), and its abilities to act as a polyclonal activator of lymphocytes and autoantibodies to various tissues and immune complexes are well known (2, 16). CD4 ϩ T cells, B cells, and plasma cells infiltrate the lungs, which is followed by further amplification of the immune response, namely, proliferation of lymphocytes, production of immunoglobulins, and release of proinflammatory cytokines (3,14). It has been previously described that the levels of total immunoglobulins, immunoglobulin A (IgA), IgM, and IgG, in serum increase during the convalescent phase of the disease (19) and that there is production of IgE specific to M. pneumoniae during infection (18). The bronchoalveolar lavage cytokine data suggest a predominant Th2-like cytokine response in M. pneumoniae infections, thus representing a favorable condition for IgE production (7), although other results suggest a Th1 cytokine response predominance (5, 21).Previous studies are confined to the acute phase of M. pneumoniae infection and do not answer questions about the possible duration of the humoral and cellular imbalance after M. pneumoniae infection in children. In this study, we hypothesized that children may have persistent abnormalities in cellular and humoral immunity development after acute M. pneumoniae infection.The study participants included 110 patients (52 male and 58 female) aged 1 to 5 years, all suffering from recurrent respiratory tract infections, defined according to Ribeiro (15). The diagnosis of M. pneumoniae infection was based on clinical symptoms (12,20) and the presence of IgM, determined by enzyme-linked immunosorbent assay (ELISA) and confirmed by PCR. Children diagnosed with M. pneumoniae infection were treated with clarithromycin (4). None of the patients had previously suffered from allergic disease or immunodeficiency syndrome. The characteristics of the patients are presented in Table 1.There were five study visits. At the first visit, patients were informed about the purpose of the study and were told that the second visit would occur after 3 months or earlier (in the case of respiratory tract infection). The patient's medical history was recorded, a physical examination was done, and blood samples for IgG, IgA, IgM, and IgE serum levels and lymphocyte phenotypes were taken at each visit. During the second visit, a blood sample was ...

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