The effect of COVID-19 infection on the white blood cell count and lymphocyte proliferation activity at the early stage of the disease

Since the appearance of COVID-19 at the end of December 2019 in Wuhan, China, and its prevalence in many countries, the symptoms of this disease extended from respiratory problems to a wide range of symptoms associated with the invasion of the virus to many organs and tissues in the body of patients. The white blood cells, particularly T lymphocytes, are the main effectors in defense against viral infections. This study was performed to investigate the response of white blood cells to the infection of SARS-COV-2 at the early stage of the disease. T cells decreased in number in the circulation, but this decrease was not associated with an impairment of their activity. Moreover, stimulation of virus-infected T cells with nonspecific mitogen revealed increased cell proliferation. This study concluded that T lymphocytes are highly activated during SARS-COV-2 infection, despite lymphopenia, at least at the early stages of the disease. Keywords: COVID-19, lymphocyte proliferation, mitotic index