Coronary artery bypass grafting is associated with immunoparalysis of monocytes and dendritic cells

Area of Science:

• Immunology
• Cardiovascular Surgery
• Critical Care Medicine

Background:

• Coronary artery bypass grafting (CABG) induces a systemic inflammatory response, potentially leading to adverse outcomes.
• Dendritic cells (DC) and monocytes are key immunoregulatory cells that may be significantly affected by CABG, resulting in an altered immune state.

Purpose of the Study:

• To investigate the dynamic changes in dendritic cell (DC) and monocyte responses following CABG.
• To assess the immune competency of CABG patients using an ex vivo whole blood culture model.
• To identify potential biomarkers for predicting adverse outcomes post-CABG.

Main Methods:

• Prospective analysis of whole blood from 49 CABG patients at five time-points: admission, peri-operative, ICU, day 3, and day 5.
• Utilized an ex vivo whole blood culture model with lipopolysaccharide (LPS) stimulation to mimic infectious complications.
• Measured co-stimulatory molecule expression, adhesion molecule expression (e.g., HLA-DR), and intracellular mediator production (e.g., IL-6) via flow cytometry.

Main Results:

• CABG significantly modulated monocyte and DC responses.
• Evidence of immunoparalysis in DCs and monocytes, characterized by a lack of response to LPS stimulation.
• This immune modulation correlated with prolonged ICU length of stay and increased incidence of post-operative atrial fibrillation.
• DC and monocyte cytokine production remained suppressed by day 5 post-surgery.

Conclusions:

• CABG induces significant modulation of DC and monocyte immune responses.
• The observed immunoparalysis in these cells is associated with adverse clinical outcomes.
• An ex vivo model assessing immune competency in CABG patients shows promise for identifying predictive biomarkers for complications.