ABSTRACTS – ORAL PRESENTATIONS - AMCA, spol. s r.o.

36. B-CELL IMMUNOPHENOTYPING OF LARGE GROUP OF COMMON VARIABLE
IMMUNODEFICIENCY PATIENTS REVEALED SUBCLUSTER WITH DISTINCT CLINICAL
FEATURES AND SIMILAR T-CELL, CYTOKINE AND GENOMIC ABNORMALITIES
Veronika Kanderova 1 , Jan Stuchly 1 , Marcela Vlkova 2 , Ivana Hermanova 1 , Ladislav Krol 1 ,
Marie Trkova 4 , Ondrej Hrusak 1 , Anna Sediva 3 , Jiri Litzman 2 , Eva Fronkova 1 , Tomas Kalina 1
1
Charles University, 2 nd Faculty of Medicine, Dpt. of Pediatric Hematology / Oncology,
CLIP-Cytometry, Prague, Czech Republic, veronika.kanderova@lfmotol.cuni.cz
2
Department of Clinical Immunology and Allergology, St Anne’s University Hospital and
Faculty of Medicine, Masaryk University, Brno, Czech Republic
3
Charles University, 2 nd Faculty of Medicine, Dpt. of Immunology, Prague, Czech Republic
4
Gennet, Genetics and Reproduction Medicine Center, Prague, Czech Republic
Common Variable Immunodeficiency (CVID) is a heterogeneous disorder of unknown
etiology. The hallmark of the disease is a humoral deficiency characterized by low
levels of serum IgG, IgA, and/or IgM, impaired specific antibody response after antigen
challenge and the resulting bacterial infections. Investigation of peripheral blood
cellular compartments revealed abnormalities in B- and T-cells. Due to a high number of
analysed parameters it is difficult to define CVID subgroups that possibly share the same
pathological mechanisms.
We have investigated detailed immunophenotype of B-cells and T-cells in CVID patients
by 8 color flow cytometry. We have used previously reported unsupervised method of
probability binning to compare distribution of cells within all possible phenotypes. Ninetyeight
patients‘ and 47 healthy donors‘ samples were used to create hierarchical tree
according to B-cell immunophenotype similarities. The cohort split into 11 phenotype
clusters and additional one with missing B-cells. Only one B-cell cluster (further
referenced as cluster_5) presented with characteristically aberrant immunophenotype
of T-cells. Cluster_5 CD4+ T-cells were reduced and presented with decreased proportion
of naive cells and increased proportion of intermediate effector memory cells (CD27-
CD28+). Increased expression of marker of exhaustion CD57, marker of anergy PD-1
and activation markers CD69 and CD70 suggested a chronic activation but activating
plasma cytokine levels (e.g. IFNg, IL-2, IL-4, IL-5 measured by bead assay) were not
elevated. Moreover, cluster_5 B-cells contained increased numbers of CD27-CD21- cells,
low number of follicular FO II cells and reduced transitional cells as compared to other
clusters.
Similar clinical presentation (autoimmunity and splenomegaly) and phenotypic profile
supported the idea of similar pathological mechanism. Whole-exome sequencing
yielded 23 possibly damaging gene alterations (single-nucleotide polymorphisms, SNP)
present in cluster_5 patients but not in controls. Minor allele variant of SNPs rs17615
and rs1048971 in CR2 (CD21) gene causing alternative splicing of exon 11 was present in
all investigated cluster_5 patients (n=6) although the frequency of minor allele in healthy
population is 27% (p