RESUMEN
<p><b>OBJECTIVE</b>To explore etiology, clinical manifestation and immunological changes of infectious pneumonia of neonates in Chengdu area.</p><p><b>METHODS</b>Serum specimens were collected from 111 infants with infectious pneumonia. Eight viral and mycoplasmal specific serum IgM antibodies were detected by enzyme linked immunosorbent assay (ELISA); C reactive protein (CRP), total IgG and its subclasses, IgA and IgM were determined by rate scattered nephelometry; T lymphocyte subpopulations were detected by biotin-streptavidin-peroxidase method, and clinical and other laboratory data were analyzed.</p><p><b>RESULTS</b>(1) Etiological agents: specific serum IgM antibodies were positive in 40 of 111 cases (36.0%) with pneumonias. All the 30 control infants were negative for the specific serum IgM antibodies. Among 111 infants with infectious pneumonia, 20.7% had single viral or mycoplasmal infection, 40.5% had bacterial infection, 15.3% had viral and mycoplasmal infection with bacterial infection; 23.4% had infection with unknown agents. (2) The most common clinical manifestations were tachypnea and cyanosis. The next were cough, milk choking, rales, retractions of the supraclavicular, intercostal and subcostal areas. Roentgenographic examination commonly revealed vague opacities, increased density and patchy infiltration. (3) Immune status: (1) CD(3), CD(4) cell counts of infants with pneumonias were lower than those of the controls while their serum IgA, IgM concentrations were higher than those of the control. (2) The CD(3) and CD(4) cell counts of the group with bacterial infection were lower than those of the control group. (3) The serum IgA concentration of the group with viral and mycoplasmal infection was higher than those of the control group and the group with unknown infection. (4) The serum IgM concentration of the group with bacterial infection was higher than those of the control group. (5) There were no significant differences in CD(8) cell counts, CD(4)/CD(8), concentration of serum IgG and IgG(1 - 4) between pneumonia group and the control group, and among various infectious groups and the control.</p><p><b>CONCLUSION</b>Pathogens of neonatal infectious pneumonia in Chengdu area included single viral or mycoplasmic infection or bacterial infection, viral and mycoplasmal infection with bacterial infection, and unknown infection. Immunological changes of newborn infants suffered from infectious pneumonia included declined CD(3) and CD(4) cell counts, particularly in bacterial infection.</p>