The Phenotypes Of Alveolar Macrophages In Bronchoalveolar Lavage Fluid Of Patients With Pulmonary Infection-related Sepsis

Background: Sepsis is the body’s dysregulated immune response to infection that can lead to tissue damage,organ failure and death.The present hypothesis of sepsis is that a hyper-inflammatory response is followed by an immunosuppressive phase during which multiple organ dysfunction is present.Macrophage is a type of white blood cell which plays an indispensable role in the innate immunity and adaptive immunity.The function of alveolar macrophage in systemic infectious diseases has attracted much attention.Objective: To observe the dynamic changes of alveolar macrophages(AMs)phenotypes in bronchoalveolar lavage fluid(BALF)of patients with pulmonary infection-related sepsis and to analyze the correlation of the two different AM phenotypes(M1 and M2)with the prognosis of the patients with sepsis.Methods: The subjects with pulmonary infection-related sepsis from intensive care unit(ICU)and department of pulmonary and critical care medicine(PCCM)of the First affiliated hospital of Bengbu Medical College were enrolled with a duration of July 2020 to December 2020.According to 28-day mortality,all patients were grouped as survival group(S group)and non-survival group(NS group).On the first day and the seventh day of admission after the diagnosis were clarified,the BALF were collected by bronchoscopy.Four color fluorescent staining method by flow cytometry was used to assess the proportion of alveolar macrophages(AMs)in BALF using the markers of CD45,CD68,CD86 and CD206.Data analysis and tabulation were acquired by SPSS 25.0 statistical software and Graph Pad Prism 8.0software.Results: 1.39 patients were included in the research span initially,and 10 cases were excluded due to the sudden death,removal of tracheal intubation and other reasons.29 patients with sepsis were included as the research subjects totally,and they were divided into survival group(n =20)and non-survival group(n=9)according to 28-day mortality.There was no significant difference of demographic data,such as age,gender and primary clinical information between S group and NS group(p>0.05).2.The morphological structures of M1 and M2 AMs were distinguishablely different.The M1 type AM have larger cell size and granularity compared with M2 type AM through flow cytometry.3.In survival group(S group,n=20),the proportion(%)of M1 and M2 in BALF was 21.39±9.91 and 4.66±2.53 respectively in the first day.In the seventh day,the proportion(%)of M1 and M2 in BALF was 3.62±3.31 and44.41±7.47 respectively.The percentage of M2 type AMs from BALF raised from the1 st day to the 7th day,while M1 type AMs declined.The difference between the two days was statistically significant in each type of cells(p<0.05).4.In non-survival group(NS group,n=9),the proportion(%)of M1 and M2 in BALF were 18.37±2.75 and 20.40±2.27 in the first day and that of 7.00±1.98 and 19.69±4.24 in the seventh day.The percentage of M1 type AMs declined from the 1st day to the 7th day,while the proportion of M2 type AMs continued higher than that of M1 type AMs.The difference of M1 type AMs between two days was statistically significant(p<0.05).The difference of M2 type AMs between two days was no statistically significant(p>0.05).5.In the first day,the difference of the percentage of M1 type AM between S group and NS group was no statistically significant(P>0.05);the proportion of M1 type AM in S group was lower than that in NS group in the seventh day and the difference between the two was statistically significant(p<0.05).The proportion of M2 AM in S group was lower than that in NS group in the first day and the result was opposite in the seventh day.The differences between the two were statistically significant both in the first day and the seventh day(p<0.05).Conclusion: The changes of alveolar macrophage phenotypes occurred in patients with sepsis.The declination of the proportion of M1 type AM and the ascension of the proportion of M2 type AM may indicate a better prognosis,but it may indicate a poor prognosis if the proportion of M2 type AM continues to be high.The changes of alveolar macrophages phenotypes are involved in the pathophysiologic process in septic patients and it plays an important role in prognostic assessment.