An emerging body of evidence suggests that half of asthma in both children and adults is associated with chronic lung infection. The aim of the present study was to determine the frequency of viable Chlamydia pneumoniae (Cp) and C. trachomatis (Ct) in the respiratory tracts of paediatric patients with chronic respiratory diseases.Bronchoalveolar lavage fluid (BALF) samples obtained from 182 children undergoing bronchoscopy for clinical reasons were assayed using PCR analysis, in vitro tissue culture and immunofluorescence staining for the presence of Cp and Ct.Chlamydia-specific DNA was detected by PCR in 124 (68%) out of 182 patients; 79 were positive for Cp, 77 positive for Ct and 32 for both organisms; 75 patients had cultivable Chlamydia. Ct DNA prevalence decreased, whereas Cp positivity generally increased with age. A total of 59 out of 128 asthma patients and 16 out of 54 nonasthmatics were Chlamydia culture positive. When the patients were divided into inflammatory versus noninflammatory airway disease, there were 69 (46%) out of 150 and six (18%) out of 32 BALF samples with cultivable Chlamydia, respectively.Viable Chlamydia pneumoniae and Chlamydia trachomatis occur frequently in children with chronic respiratory diseases and may be more prevalent in asthma patients. To the current authors' knowledge, this is the first report of viable Chlamydia trachomatis in the lungs of children.

Summary This study examined the effect of thymoglobulin induction therapy on leukocyte population dynamics in kidney transplant patients. Patients receiving standard immunosuppression were compared with those who received additional thymoglobulin at the time of kidney transplantation. Thymoglobulin induction led to an immediate and significant decrease of all T cells and NK cells, but not B cells or monocytes. CD8+ T cells recovered to near pretransplant level by 4 weeks post‐transplant. CD4+ T cells remained at less than 30% of pretransplant level for the entire study period of 78 weeks. Both CD4+ and CD8+ T cells showed reduced cytokine production after recovery. Deletion of CD4+FOXP3+HELIOS+ regulatory T cells (Tregs) was less profound than that of CD4+FOXP3− cells, thus the relative percentage of Tregs elevated significantly when compared with pretransplant levels in thymoglobulin‐treated patients. In contrast, the percentages of Tregs and their expression of FOXP3 in the standard immunosuppression group decreased steadily and by 12 weeks after transplant the average percentage of Tregs was 56% of the pretransplant level. Thus, thymoglobulin‐induced deletion of T cells led to significant and long‐lasting alterations of the T‐cell compartment characterized by a preservation of Tregs and long‐lasting reduction in CD4+, and potentially pathogenic, T cells.

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