Double positive T lymphocytes do not vary in different age groups in Colombian Blood Donors

To the Editor, We have read with interest the letter of Marini et al, 2020 about the percentages and absolute numbers of double positive T cells (DPTs) in peripheral blood of a normal Italian population. In a previous article by our group (1), the DPTs population was evaluated in one hundred suitable donors from a Colombian blood bank using flow cytometry. Our main findings showed a median of DPTs of 2.6% and a higher percentage in women. In the Italian cohort, they found an increase of DPTs with age and no difference by gender. In our study, we did not test donors over 61 years old to corroborate if age is associated with the marked increased level of DPTs above this age as shown in the Italian population. We reanalyzed our data and did not find a difference in the percentages of DPTs when comparing age groups (Figure 1). In the Spanish and German cohorts, although there is no significant difference of DPTs according to gender, women showed a tendency to have more DPTs when compared to men (2,3). The flow cytometry panel (monoclonal antibodies and fluorochromes) used in our work detected and discriminated the DPTs through manual gating as shown in the publication (1). Previous studies show that the antibody cocktail and the gating strategy (manual versus automated) are sources of variability in the results (4). Also, according to the flow cytometry analysis showed (1), it was possible to determine the subpopulations of CD4highCD8low and CD4lowCD8high in healthy donors as described by other authors (5,6). In order to understand the differences found in the publications, future studies must include a more diverse population, larger samples, and increased age range.


To the Editor,
We read with interest the letter of Gonzalez-Mancera et al. [1] regarding the percentages and absolute numbers of doublepositive T cells (DPTs) in the peripheral blood of a normal Italian population. In a previous article by our group, the DPT population was evaluated in one hundred suitable donors from a Colombian blood bank using flow cytometry. Our main findings showed a median DPT value of 2.6% and a higher percentage in women.
In the Italian cohort, they found an increase of DPTs with age and no difference by sex. In our original study, we did not test donors over 61 years old to corroborate if age is associated with the marked increased level of DPTs above this age, as shown in the Italian population. We reanalyzed our data and did not find a difference in the percentages of DPTs when comparing age groups ( Figure 1).
In the Spanish and German cohorts, although there was no significant difference in DPTs according to sex, women showed a tendency to have more DPTs when compared to men [2,3].
The flow cytometry panel (monoclonal antibodies and fluorochromes) used in our work detected and discriminated the DPTs through manual gating as shown in the original publication [1]. Previous studies showed that the antibody cocktail and the gating strategy (manual versus automated) are sources of variability in the results [4]. Also, according to our original flow cytometry analysis [1], it was possible to determine the subpopulations of CD4 high CD8 low and CD4 low CD8 high in healthy donors as described by other authors [5,6].
In order to understand the differences found in these publications, future studies must include a more diverse population, larger samples, and increased age range.

To the Editor,
We read with great interest the recently published article in your journal by Kaya et al. [1] regarding a novel mutation in the Wiskott-Aldrich syndrome (WAS) gene. After that publication, we also had a patient with another novel mutation in the WAS gene from Turkey.
A 3-month-old boy was admitted to our hospital with the complaints of cough, wheezing, and eczema. He also had a history of pneumonia. On physical examination, diffuse eczema was observed (Figure 1), along with widespread petechiae and pulmonary crepitant rales and rhonchi. His family history was unremarkable. Laboratory analysis revealed anemia (hemoglobin of 8.9 g/dL), leukocytosis (white blood count of 13,330/mm 3 ), and thrombocytopenia (platelet count of 63,000/mm 3 ). Mean platelet volume was 4.8 fL. A peripheral blood smear revealed thrombocytopenia and micro-thrombocytes. Immunoglobulin levels were normal. Peripheral lymphocyte subset analysis revealed reduced CD3 percentage and CD16/CD56 ratio. With these results, patient was diagnosed with WAS, and molecular genetic analysis revealed a novel mutation in the WAS gene, a hemizygous c.11_12insGG p.G4Afs mutation on exon 1 ( Figure  2). The patient is 18 months old now. Human intravenous immunoglobulin therapy was administered monthly, and thrombocyte replacement was done in case of need [2]. He did not have a family donor, so he was scheduled for allogeneic hematopoietic stem cell transplantation from an unrelated donor.