New Insights into Blood Circulating Lymphocytes in Human <i>Pneumocystis</i> Pneumonia

• Main Authors: Eléna Charpentier, Catherine Marques, Sandie Ménard, Pamela Chauvin, Emilie Guemas, Claire Cottrel, Sophie Cassaing, Judith Fillaux, Alexis Valentin, Nicolas Blanchard, Antoine Berry, Xavier Iriart
• Format: Article
• Language: English
• Published: MDPI AG 2021-08-01
• Series: Journal of Fungi
• Subjects: <i>Pneumocystis jirovecii</i>; pneumocystosis; immunophenotyping; lymphocyte; T helper; B lymphocytes
• Online Access: https://www.mdpi.com/2309-608X/7/8/652

The host lymphocyte response is decisive in <i>Pneumocystis</i> pneumonia (PCP) pathophysiology but little is known of the specific roles of lymphocyte subpopulations in this fungal infection. Peripheral NK, NKT, B, TCD4+ and TCD8+ subpopulations were compared by immunophenotyping between 20 patients diagnosed with PCP (PCP(+)] and 20 uninfected immunosuppressed patients (PCP(−)). Among PCP(+) subjects, the lymphocyte populations were also compared between surviving and deceased patients. Low B cell count (<40 cells/µL) was more frequent in PCP(+) than in PCP(−) patients (<i>p</i> = 0.03), while there was no difference for the TCD4 count. Among the PCP(+) group, the 7 deceased patients had lower Th1 (<i>p</i> = 0.02) and Tc1 (<i>p</i> = 0.03) populations, higher Th2 response (<i>p</i> = 0.03), higher effector TCD8 (<i>p</i> < 0.01), lower central memory TCD8 (<i>p</i> = 0.04) and reduced NK cells (<i>p</i> = 0.02) compared with the 13 survivors. Th1/Th2 ratio < 17, CD8 Tc1 < 44%, effector TCD8 < 25%, central memory TCD8 < 4%, NK cells < 50 cells/µL and total lymphocytes < 0.75 G/L were associated with a higher risk of mortality (<i>p</i> = 0.003, <i>p</i> = 0.007, <i>p</i> = 0.0007, <i>p</i> = 0.004, <i>p</i> = 0.02 and <i>p</i> = 0.019, respectively). The traditional analysis of TCD4 and TCD8 populations may be insufficient in the context of PCP. It could be completed by using B cells to predict the risk of PCP, and by using lymphocyte subpopulations or total lymphocyte count, which are easy to obtain in all health care facilities, to evaluate PCP prognosis.