Immunological parameters associated with the severity of COVID-19 pneumonia in kidney transplant recipients

An outbreak of a novel respiratory disease due to coronavirus species was emerged in 2019 and named as Coronavirus Disease-2019 (COVID-19). Clinical and immunological factors affecting the course of COVID-19 in kidney transplant recipients (KTR) are not well-known.

In this prospective observational study, we presented 20 KTR with COVID-19 pnemonia and examined the factors predicting the severity of COVID-19. A total of 10 KTR without COVID-19 was used as control group. Lymphocyte subsets were determined by flow cytometry. In 13/20 patients, immunophenotyping was repeated 1 week later.

Mean age of the patients was 50 ± 9 years. Patients were classified as mild-moderate (oxygen saturation: SO₂ > 90%) and severe disease groups (SO₂ ≤ 90%). Serum albumin and hemoglobin were lower and CRP, fibrinogen and peak D-dimer were higher in severe group. Peak CRP was inversely associated with nadir SO₂ (r =  - 0.68, p = 0.001). Neutrophil/lymphocyte ratio was higher in severe group (p = 0.01). CD3 + and CD4 + cells were lower and NK cell percentage (CD16 + 56 +) was higher in severe group. Percentage of spontaneously activated CD8 cells (CD8 + CD69 +) was higher in severe group. In comparison of KTR with and without COVID-19, CD8 + cells were lower but NK cell percentage was higher in KTR with COVID-19.

In this pilot study, increased NK cells, activated CD8 + cells and decreased CD3 + and CD4 + cells were associated with severity of COVID-19 in KTR. Peripheral immunophenotyping of lymphocyte subtypes may provide prognostic information about the clinical course of COVID-19 in KTR.