[Expression and clinical significance of lymphocyte subsets in infectious pneumonia and immune-related interstitial lung disease].

OBJECTIVE

To delineate differences in lymphocyte subset expression between patients with infectious pneumonia and immune-related interstitial lung disease (IRILD), to assess the immune status across distinct pneumonia types, and to provide novel laboratory markers through immunological profiling to effectively differentiate pneumonias.

METHODS

A total of 78 patients sequentially enrolled from Peking University People' s Hospital between January 2023 and March 2024 were stratified into three groups: 27 with infectious pneumonia, 27 with isolated immune-related interstitial lung disease (IRILD), and 24 with IRILD complicated by infection. Fifty age-matched healthy individuals undergoing routine physical examinations during the same period served as controls. Peripheral lymphocyte subsets were quantified in all subjects by multiparametric flow cytometry.

RESULTS

There was no statistically significant difference in age between the pneumonia patients and the healthy control group in this study (P>0.05). Analysis of laboratory parameters revealed that compared with the IRILD group, the infectious pneumonia group demonstrated significantly elevated levels of neutrophils, C-reactive protein, procalcitonin (PCT), erythrocyte sedimentation rate (ESR), D-dimer, and fibrinogen (P < 0.05), while the IRILD with superimposed infection group exhibited significantly increased levels of PCT, ESR, and immunoglobulin G (P < 0.05). At the lymphocyte subset level, compared with the control group, the infectious pneumonia group exhibited significantly decreased counts of T cells, B cells, natural killer (NK) cells, CD4+T cells, and the CD4+/CD8+ ratio (P < 0.05). Similarly, compared with the control group, the IRILD group showed significantly reduced counts of T cells, B cells, CD4+T cells, and the CD4+/CD8+ ratio (P < 0.05). Furthermore, compared with the control group, the IRILD-with-infection group demonstrated significantly lower counts of T cells, B cells, NK cells, CD4+T cells, and CD8+T cells (P < 0.05). Compared with the IRILD group, the infectious pneumonia group had a significantly lower NK cell count (P < 0.05). Additionally, compared with the IRILD group, the IRILD-with-infection group displayed significantly reduced counts of NK cells and CD8+T cells (P < 0.05).

CONCLUSION

The study revealed significant variations in lymphocyte subset profiles among the distinct pneumonia groups, providing novel insights with potential diagnostic value for differentiating between pneumonia types.