Objectives: Coronaviruses (CoV), known to exist for about 70 years, were considered animal pathogens in the 1930s. By the 1960s, they were also defined as human respiratory pathogens. Since then, CoVrelated epidemic diseases called Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS) and finally Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) have emerged. In this study, it was aimed to determine the phenotypic characteristics of the host cells involved in the immune response against SARS-CoV-2.

Material and Methods: A total of 54 COVID-19 patients between the ages of 18-71 were included in this study. Immunophenotype analyzes of T cells, B cells, Natural Killer (NK) cells, monocytes and monocyte-platelet aggregation were measured by flow cytometry method using the FACSCalibur (Becton Dickinson, San Jose, CA, USA) device.

Results: While a decrease in the lymphocyte count was observed in 25.9% of the patients, the lymphocyte count was within the normal range in 74.1%. CD3+ T-lymphocyte ratio 73.96 ± 7.96%, CD4+ CD3+ T-Helper (Th) expression 45.06 ± 10.22%, CD8+CD3+ T-cytotoxic (Tc) expression 25.72 ± 8% It was found to be 58. CD4 / CD8 ratio was calculated as 1.89 ± 0.85. CD19+ B lymphocyte ratio was 9.82 ± 4.45% and CD56+ expression was 14.38 ± 6.28%. The lymphocyte HLA-DR ratio was 16.41 ± 7.50%, and the HLA-DR ratio in monocytes was 92.31% (76.24-95.53). CD61 expression in monocytes was 26 ± 13.95%. A negative correlation was found between CD61 in monocytes and HLA-DR (r = - 0.347).

Conclusion: The findings we obtained in our study, in which we looked at the immunophenotype characteristics of T, B, NK and monocyte cells of COVID-19 patients, do not seem to be significant. However, the CD61 increase in monocytes, the inverse correlation between HLA-DR in monocytes and CD61, was thought to be significant considering the thrombotic complications reported in COVID-19 patients.