Comparison of T Lymphocyte Subsets and Natural Killer Lymphocytes in Moderate Versus Severe COVID-19 Patients.

Severe respiratory involvement that follows a process of immune dysregulation and intense cytokine production remains to be the most dreaded complication of Coronavirus Disease-2019 (COVID-19) infection. The aim of this study was to analyze T lymphocyte subsets and natural killer (NK) lymphocytes in moderate and severe cases of COVID-19 infection and assess their significance in disease severity and prognosis. Twenty moderate cases and 20 severe cases of COVID-19 were studied and compared regarding blood picture, biochemical markers, T lymphocyte population subsets, and NK lymphocytes, which were determined by flow cytometric analysis. On analyzing the flow cytometric data of T lymphocyte cells and their subsets and NK cells in two groups of COVID-19 infection (one group moderate and the other severe cases), some immature NK lymphocyte relative and absolute counts were higher in the severe patients with worse outcome and death, while some mature NK lymphocyte relative and absolute counts were depressed in both groups. Also, interleukin (IL)-6 was significantly higher in severe cases when compared to moderate cases, and there was a positive significant correlation between immature NK lymphocyte relative and absolute counts and IL-6. There was no statistically significant difference between T lymphocyte subsets (T helper and T cytotoxic) with disease severity or outcome. Some immature NK lymphocyte subsets contribute to the widespread inflammatory response that complicates severe cases of COVID-19; therapeutic approaches directed to enhancing NK maturation or drugs that block NK cell inhibitory receptors have a potential role in controlling COVID-19 induced cytokine storm.

Changes in peripheral blood cellular morphology as diagnostic markers for COVID-19 infection.

INTRODUCTION: Real-time reverse-transcriptase polymerase chain reaction (RT-PCR) assays were established to detect severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2). However, due to the high rate of false negative results, additional tests as computed tomography (CT) scans of the chest and blood chemistry are required to properly diagnose COVID-19 infection. Abnormal morphological changes of peripheral blood cells as granulocytic dysmorphism and abnormal reactive lymphocytes have been described in some cases. The aim of the present study was to investigate the morphological changes affecting all peripheral blood cells of COVID-19 patients, in order to find any specific abnormalities that could help in the early diagnosis and/or prognosis. METHODS: Peripheral blood smears of 113 COVID-19 patients and 50 non-COVID-19 controls were examined for morphological changes in the period between October 2020 and January 2021 (second wave). We set a score value in which every morphological abnormality was given one point in each examined blood smear. Score, neurophil/lymphocyte (N/L) ratio, and blood chemistry were compared to the severity and outcome of the disease. RESULTS: Significant morphological changes were found when compared to control blood smears. Various abnormalities as pyknotic cells, broken cells, pseudo Pelger-Huët, abnormal lymphocytes, abnormal monocytes, and leukoerythroblastic reaction were found. Cases with higher scores had unfavorable outcomes (p = .005). High interleukin-6 (IL-6) levels were correlated to pyknotic cells (p = .003). CONCLUSION: The blood picture of COVID-19 patients revealed various morphological changes that are not detected with the same frequency and variability in other viral infections. The prominent morphological changes can be predictive of an undesirable outcome of the disease.