engleski

A case study of primary immunodeficiency: an unusual phenotype of a selective IgA deficiency patient unveiled by polychromatic flow cytometry

Background: Primary immunodeficiencies (PID) are heterogeneous disorders caused by defects of innate and/or adaptive immune system, with antibody deficiencies i.e. selective IgA deficiency being the most common form of PID affecting 1/600 individuals in the western world. Dysfunctional antibody production stems from inherited defects of B-cell differentiation and maturation. Due to the lack of IgA antibodies at mucosal surfaces, patients with selective IgA deficiency suffer from recurrent sinopulmonary and gastrointestinal infections, and have an increased risk of autoimmune and allergic diseases. Patient and method: A 13 year-old male patient diagnosed with selective IgA deficiency presenting with recurrent respiratory infections, allergic asthma, allergic rhinitis, gastrointestinal disturbances and epilepsy has been followed up at our hospital for several years and subjected to routine immunophenotyping with a suspicion of common variable immunodeficiency (CVID) - another form of antibody deficiency disorder with an insufficient IgG, IgA and IgM antibody production and the consequent recurrent infections, which may develop from selective IgA deficiency. Flow cytometry immunophenotyping of peripheral blood was performed for the analysis of T cells, NK cells and B cells using 6- and 7-colour antibody panels against the CD3, CD4, CD8, CD16, CD19, CD24, CD27, CD38, CD45, CD56, HLA-DR, IgD and IgM surface markers. Acquisition of the samples was performed using the Navios flow cytometer (Beckman Coulter, USA) and the data was analyzed using the FlowLogicTM software (Inivai Technologies, Australia). Results: A prominent immunophenotypic feature was the appearance of a CD3dim population which was also identified as CD8+, CD16+ and CD56dim. The percentage of the CD3dim population showed an increasing trend during 3 consecutive immunophenotyping within one year: approx. 3.5% to 6.5% of total lymphocytes, variable in size and granularity. Immunophenotyping also showed low relative and absolute values of class-switched memory B cells, double negative B cells and plasmablasts of the patient compared to the reference values of the respective age, which were constant over time. A decrease was noted in the frequency of the NK cell population where the CD16+CD56- fenotype dominated. Conclusion: We report an existence of a peculiar CD3dimCD8+CD16+CD56dim population from the PID patient diagnosed with selective IgA deficiency who otherwise exhibits the lack of terminally differentiated B cells - an immunoprofile typical of the disease. No other paediatric PID patient admitted to our routine immunophenotyping emerged with this unusual phenotype. Low number of NK cells has recently been associated with a severe form of CVID. However, further monitoring and diagnostic tests are needed to associate the accompanying NK cell decrease and the patient's clinical profile with a possible CVID diagnosis, and, in particular, to unravel the characteristics of the CD3dim population and its clinical relevance.

PID, IgA, Flow cytometry

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