Exploración del Inmunofenotipo de las Subpoblaciones Linfocitarias B y T como posibles Biomarcadores en la Intersección entre Inmunodeficiencia Primaria y Secundaria en Pacientes con Linfoma no Hodgkin

Primary immunodeficiencies (PIDs) are a heterogeneous group of diseases with alterations in any component of the immune system, and characterized by recurrent or severe infections, autoimmune diseases and cancer. Within PIDs, common variable immunodeficiency (CVID) is the most common symptomatic PID, with an incidence of 1/25.000 population. It is distinguished by impaired antibody production and decreased class switching memory B-cell counts. In addition, in recent years it has been reported that patients with CVID also have shared alterations in the T helper (Th) lymphocyte compartment. Secondary immunodeficiencies (SIDs), on the other hand, are acquired immune disorders resulting from an underlying condition or from drugs used, for example, to hematological malignancies and their treatments. PID and SID are associated with an increased risk of infections, immune dysregulation, autoimmune disorders, lymphoproliferative syndromes and malignancy. In a yet unknown proportion of cases, immunodeficiencies that are initially attributed to secondary causes are actually due to an underlying PID. These patients may have more severe infection, more toxicities to current therapies for cancer, and other consequences for the patients and their families. Thus, it is important to search for new biomarkers at the intersection of PID and SID in patients with hematological malignancies, such as non-Hodgkin's lymphoma (NHL). An early diagnosis of PID may allow a more appropriate treatment to be established, allowing a better prognosis of the disease, as well as the study of family members and genetic counselling. Previous studies by our group have already established a few markers that may contribute to the diagnosis of PID in patients with hematological malignancy, including clinical history of recurrent/severe infections during childhood or years before cancer, autoimmune diseases, as well as immunological variables at the time of lymphoma diagnosis, absence of immune reconstitution after treatment, response to anticancer therapy and genetic studies, among others. The aim of this study is to determine whether immunophenotyping of B and Th lymphocyte subpopulations by multiparametric flow-cytometry can add value as a biomarker at the intersection between PID and SID in NHL patients. For this purpose, we enrolled 71 patients with NHL, and classified them into the "Suspected PID" and "SID"-Groups according to the latest clinical criteria for the diagnosis of CVID of the European Society for Immunodeficiency Diseases. We then proceeded to the comparative analysis of 37 immunological and clinical variables. We also evaluated 12 subpopulations of B cells, covering their entire maturation process, as well as 11 CD4+ T cell subpopulations comprising the different subsets of Th. In addition, we performed a supplementary study to observe further differences in B and Th immunophenotypes. To do this, we classified patients according to the sum of kappa and lambda light chains, 20 mg/dL or less being considered suspicious for CVID, while a score of more than 20 being considered suspicious for SID. In terms of the results obtained, significant statistical differences were observed between the "Suspected CVID" and "SID" groups in 4 of the 37 variables analyzed, including one clinical and three laboratory biomarkers. Recurrent and/or severe infections during childhood were higher in patients with suspected PID, while IgM levels at NHL diagnosis, as well as sum of kappa and lambda light chains and class switching memory B-cell levels were lower. In terms of immunophenotypes, the supplementary study showed that the frequencies of class switching memory B cells, plasmablasts and Th17 cells were statistically lower in the “Suspected CVID-Group” than in the “SID-Group”. These results suggest the presence of defects in the B cell maturation process as well as in the Th compartment and in the interaction between the two compartments in patients with suspected CVID. In conclusion, identifying significant clinical and immunological variables may help in the difficult task of recognizing late-onset PID among patients with SID to hematological malignancy. For this reason, our preliminary data point to the added value of memory B cell and Th phenotype in this difficult task. Prospective studies in larger cohorts are warranted to validate the results obtained and confirm the observed trends.