Monitoring of Immune Memory by Phenotypical Lymphocyte Subsets Identikit: An Observational Study in a Blood Donors’ Cohort

The cross-talk between the innate and adaptive immune response represents the first defense weapon against the threat of pathogens. Substantial evidence has shown a relationship between immune phenotype lymphocytes and COVID-19 disease severity and/or implication in susceptibility to SARS-CoV-2 infection. Recently, belonging to ABO blood groups has been investigated as a correlation factor to COVID-19 disease. This pilot study investigated lymphocyte typing in a cohort of blood donors to understand the underlying mechanism in SARS-CoV-2 infection linked to the blood group. The study cohort consisted of 20–64-year-old subjects, without comorbidities, from both sexes, who were COVID-19 vaccinated with previous or no infection history. Whole blood samples, collected at A.O.R.N. Sant’Anna and San Sebastiano Hospital (Campania Region), were processed by multiparametric cytofluorimetric assay, to characterize CD4+ helper and CD8+ cytotoxic T cell CD3+ subpopulations. The CD45RA, CCR7, CD27, CD28, CD57 and PD-1 markers were investigated to delineate the peripheral T-cell maturation stages. Differences were detected in ABO blood types in CD3+, CD4+ gated on CD3+, CD8+ and CD8+ gated on CD3+ percentage. These results contribute to identifying a memory cell “identikit” profile in COVID-19 disease, thus leading to a useful tool in precision medicine.