Lymphocyte Population Changes at Two Time Points during the Acute Period of COVID-19 Infection.

We previously observed an increase of serum interleukins (IL) and a reduction of most lymphocyte subpopulations in hospitalized COVID-19 patients. Herein, we aimed to evaluate the changes in serum IL-6, IL-10, and IL-17A levels and cytometric lymphocyte profiles in 144 COVID-19 patients at admission and after one week, also in relation to steroid treatment before hospitalization. After one week of hospitalization, we found that: (i) total lymphocytes were increased in all patients; (ii) neutrophils and IL-6 were reduced in mild/moderate patients; (iii) B lymphocytes were increased in severe patients; (iv) T lymphocyte populations increased in mild/moderate patients. In the eight patients that died during hospitalization, total leukocytes increased while T, T helper, T cytotoxic, T regulatory, and NK lymphocytes showed a reducing trend in five of the eight patients. Even if seven days are too few to evaluate the adaptive immunity of patients, we found that the steroid therapy was associated with a reduced COVID-19 inflammation and cytokine activation only in patients with severe disease, while in patients with less severe disease, the steroid therapy seems to have immunosuppressive effects on lymphocyte populations, and this could hamper the antiviral response. A better knowledge of cytokine and lymphocyte alterations in each COVID-19 patient could be useful to plan better treatment with steroids or cytokine targeting.