gms | German Medical Science

Objectives: Sepsis is a life-threatening condition, associated with a high mortality rate. It is defined as organ dysfunction caused by an abnormal host immune response to an infection (Sepsis-3). Previously it has been shown that sepsis leads to immune suppression ("immune paralysis"), characterized by lymphocytes exhaustion and apoptosis. Therefor we investigated the pattern of the immune cells 3 days and 14 days after sepsis induction in the abdominal lymph nodes and spleen. We also analyzed the expression of Programmed cell death protein 1 (PD-1) and the function of the lymphocytes isolated from abdominal lymph nodes 14 days after sepsis induction.

Methods: The cecal ligation and puncture (CLP) mouse model was performed to induce sepsis. Sepsis mice and control animals, which received only an abdominal incisure, without cecal ligation and puncture, were monitored for 3 days (n=6) and 14 days (n=5). Afterwards the mice were sacrificed, the abdominal lymph nodes and the spleen were harvested. Cells of lymph nodes and spleen were isolated using the enzymatic digestion and analyzed by flow cytometry using the following antibodies: CD220, Ly6G, TCR beta, TCR gamma/delta, CD45 and PD1. The cells of abdominal lymph nodes isolated 14 days after the sepsis induction were stimulated for 3 days as following: LPS (100 ng/ml); IL-2 (20 pg/ml) and no stimulation (negative control).

Results and Conclusion: Macroscopically a significant enlargement of the abdominal lymph nodes after 3 and 14 days of sepsis was observed. 3 days after the sepsis induction, a decrease of the CD220 and TCR beta, and an increase of Ly6G and TCR gamma/delta positive cells was detected in the abdominal lymph nodes tissue. 14 days after the sepsis induction, in the abdominal lymph nodes, an increase of CD220, Ly6G, TCR gamma/delta, CD45, PD-1, and a decrease of TCR beta positive cells was observed. However, in the spleen, 14 days after the sepsis induction, a decrease of CD220, TCR beta, and CD45, and an increase of Ly6G, TCR gamma/delta, PD-1 positive cells could be detected. The cell stimulation assay revealed a decrease of PD-1 expression after LPS (100 ng/ml) stimulation. However, IL-2 had no effect on PD-1 expression of the lymphocytes from the abdominal lymph nodes.

Sepsis is accompanied by a depletion of the TCR beta positive cells in the peripheral lymphatic organs and an increase of lymphocytes exhausting markers (PD-1). Moreover, an increase of TCR gamma/delta and Ly6G positive cells were observed in the abdominal lymph nodes, as well as in the spleen. CD220 and CD45 showed an organ specific detection pattern, being increased in the lymph node and decreased in the spleen.