May be dysfunction of cellular immunity considered a sign of post-COVID syndrome?

Our aim was to study association between proliferative activity of peripheral blood lymphocytes after COVID, and developing post-COVID syndrome, and to determine whether the cell immunity dysfunction may be regarded as its marker. The retrospective cohort study involved 242 patients (56 males, 186 females, 18 to 85 years old) who contracted new coronavirus infection. Of them, post-COVID syndrome was diagnosed in 180 cases (duration over 3 months). The patients were classified by severity of clinical course of COVID (i.e., presence of acute respiratory disease and pneumonias), and PHA-induced blast transformation of lymphocytes. Along with PHA-induced response, we studied cyclooxygenase (COG)-producing cells by morphological method. Control group consisted of 200 healthy people without any features of coronavirus infection. All patients were questioned and examined by multidisciplinary medical team, dependent on their complaints. We also registered incidence of comorbidities associated with cellular immune deficiency. The patients with post-COVID syndrome exhibited a decrease of PHA-induced lymphocyte proliferation as compared with control group (significant at p 0.01 in cases of acute respiratory infection, and p 0.05 in patients with pneumonia). Activity of COG-producing cells was similar in all groups, independently on presence of post-COVID syndrome. Classification of patients by presence of cellular immune dysfunction (PHA-induced blast transformation 50%) allowed to detect higher activity of COG-producing cells. This enzyme is known to participate in development of inflammation promoting immune deficiency, thus, probably, manifesting in clinical activation of herpesvirus infection following COVID-19. Activity of COG-synthesizing cells was found to be higher in post-COVID syndrome which evolves after middle-severe and severe forms of new coronavirus infection complicated by pneumonias. Chronic inflammation in post-COVID syndrome associated with high activity of COG-producing cells may promote dysfunction of cell immunity, thus being a cause of evolving syndrome, like as its biomarker. Absence of the immune cell dysfunction markers among other post-COVID features leads to decreased registration of post-COVID patients and misinterpretation of the results obtained.