The difference of T lymphocyte subsets between mild type and severe type in patients infected with the 2009 pandemic influenza A (H1N1) virus and its clinical significance

Objective To study the changes of subgroups of peripheral blood T lymphocytes in the patients infected with the 2009 pandemic influenza A ( H1N1 ) virus of different severity type. Method A total of 66 patients infected by H1N1 evidenced by RT-PCR admitted from September 2009 to January 2010 were divided into three groups: mild type ( B group, n = 47 ), cured patients of severe and critical severe type ( C group, n = 14) and died patients ( D group, n =5), according to the severity and prognosis. A total of 20 healthy volunteers served as control group( A group). Peripheral blood lymphocyte count, CD3+,CD4+ and CD8+ T lymphocyte count were detected by flow cytometry at the different time points. Fever duration and H1N1 virus negative time were compared. Statistical analysis were performed by using SAS version 9.13 software and the data were processed with ANOVA and SNK test. Results Lymphocyte count, CD3+,CD4+ and CD8+ T lymphocyte count declined in the early period in all the groups, and there were significant differences compared with A group (P＜0. 05), while rised with the clinical progression in group B and C,and those of C group were lower than B group ( P ＜ 0.05 ), but those of D group were always low. Fever duration and H1N1 virus negative time were (4.4 ± 1.6) days vs. (4.4 ± 1. 4) days, ( 12.9 ± 3. 1 ) days vs.( 10.2 ± 2.6) days and ( 15.2 ± 7.3 ) days vs. ( 13.3 ± 2.9 ) days respectively, and there were significant differences among the three groups ( P ＜ 0.05 ). Conclusions The cellular immune function was seriously damaged when patients were infected with H1N1. Further more, the changes of lymphocyte count, CD3+ , CD4+and CD8+ T lymphocyte count were tightly related with the degree of severity and prognosis. These findings can be used for clinical diagnosis and treatment. Key words: H1N1 Virus; Lymphocyte; T lymphocyte subsets; CD4+ T lymphocyte; CD8+ T lymphocyte; Flow cytometry; RT-PCR